Unless that army is IG...5" blast with str10 ap2?

Argh don't tempt me to switch armies like that I can barely afford to support my cadre!
But I guess I should have expected that kind of firepower from them. Some may argue that we're the kings of ranged combat but nothing can outgun an IG artillery regiment.

The problem is that none of those get through his FNP and his Invuln save. After taking the 5+ invuln and the 4+ FNP even a good 30+ wounds will only kill a few boyz at best. The markerlight pinning tests don't help untill there are only 10 boyz left thanks to mob rule, a rule that makes their leadership=to the number of boyz in the unit. If he has more than 10 orks they're fearless making pinning useless. Also, since when do markerlights give more shots? You're probably talking about letting more shots hit as opposed to actualy shooting more. I might just ignore that group untill the rest of his army is gone. It shouldn't take much shooting to kill his smaller boyz groups and his tankbustas. His whole army is pretty slow so avoiding the big unit shouldn't be much trouble if I work on my actualy USING our great mobility.
Note to self, get another devilfish.

Railhead Submunition sounds like what the doctor ordered here.
I would have to check, but I believe it's double-toughness strength at normal Orks, which negates FNP. Can't get rid of the 5+ Invul, but that's kinda the point. With a large blast template, we should be putting out enough shots.

The real issue is having to deal with other armies at the same time. Thus, I wouldn't recommend three Hammerheads, maybe two at most. (My preferred is one Hammerhead.) My strong recommendation is to invest in Missile Pods. They are also double-toughness strength, and require them to use their cover/invul saves instead, and you can strip cover with markerlights, AND you get an average number of shots AND you get range AND they're cheap. (In a vacuum, those missile pods are the single most useful weapon in the army, there is very little they AREN'T effective against. (Paladins. Grr.))

Orks are T4, MP and Submunitions are str 7 and 6 respectively.

Also, last time I checked, ork boyz do not have a 5+ invul save...

They are using a Kustom Force Field probably. A mech boy thrown in can give them that, or I think cybork parts also confer the 5+ invul. They normally have 6+ armor if I recall.

Not the kustom force field, they have cybork bodies wich gives the invuln save. KFF is a cover save, we have markerlights for that.

Well how often do you see an entire horde of ork boyz all equipped with cybork parts? Is that even legal?

It's not somthing to worry about.

That is what his opponent is using. =P

With Mad Dok Grotsnik you can give any unit cybork bodies for the same cost as a multi-tracker per model.

Yah, I never said it was a common problem. His fellow ork players think he's crazy for trying it when he tells them. I just got another hammerhead that should help solve the problem but I won't know for sure untill I get it painted and battle-ready. I'll let you guys know how it goes but it might be a while, I'm not a very fast painter.

If his orks cost that much per model, then the slightly dampened damage would still be reaping as many points, or more, form them. It means his "horde" would barely deserve the title, as it would be half as many orks as normal. All for inv. flak armour.

Also, that means that you only need to spend one token and lower his cover save to 5+ bs5 anyone?

Grotsnik should also be what is giving them the feel no pain rule (he is likely joined with the squad). He also confers rage to that unit which makes them extremely easy to kite or bait the unit away from the rest of your army with a few surviving kroot.

Dealing with the unit shouldn't be too difficult, 5+/4+ gives them the durability of marines (it's effectively a 3+ save) which certainly means the unit is annoying to remove, but it's so dang expensive that his army cannot have much else.

Take flechette dischargers on a sacrificial vehicle and put it close to the unit, he will be forced to assault it and take fairly significant casualties. Props if you can position the vehicle in such a way that it runs the squad away from your army (should be easy with a flat out move from a piranha).

Rage sucks, abuse it.

I have just had a 1750pts game against an ork army, he took:
a battle wagon + deth roller with a mek (with Kustom Force Field) and 19 boyz + power klaw inside (I think 19 boyz in the battle wagon may have been less, but I didn't count them),
a squad of lootas (15 strong),
3 killa kanz (single squad) - kept next to the battle wagon to take advantage of the KFF,
2 squads of 3 war traks,
1 squad of deth kopters - out flanking
4 attack bikes + mad doc + big nob on a bike.
1 mob of 20 boyz on foot + power klaw

My list was just a modified version of a list I had taken expecting to go up against a 1500 space puppies force (in rhinos + whirl wind + drop pod).
shas'el with FB + PR + shield
2 squads of 3 broad sides (SMS + MT) + 1 shield drone per squad
2 squads of 2 piranhas (FB)
3 squads of 6 FW with war fish
1 montat T/L flamer + Burst canon
1 rail head +BC

Playing kill points and long edge deployment.

Between the bikes 3+ turbo boost save, 4+ smoke and their FNP (from the mad doc), the meks 5+ KFF (bubble protecting kanz and battle wagon) he lost almost as many vehicles through failed dangerous terrain tests as he did through my shooting.
The most effective unit was the montat which deep striked just behind the foot slogging boyz and killed 9 boyz with the flamers and 1 with the burst cannon, before the rest of the squad turned around and hit him with the power klaw (I said for him to just roll the klaw, it hit and killed the suit rather than rolling 30+ dice for boyz on the charge in a Waaargh! turn).
In the future I'd drop the fish and take more flamer/BC suits, probably be more effective, or even T/L flamer + fusion blaster.

I declared on turn 4 as 1 squad of piranhas, 1 squad of broad sides, the rail head, 2 war fish and 2 fire warrior squads were dead,
the rest of my army was either in combat, about to be in combat or ( in the case of the surviving piranhas, one of which only had the drones) the other side of the board.
I managed to take out 3 lootas, 10 boyz, 1 killa kan and 3 traks, his bad terrain rolls killed off 2 bikes and 2 traks.

One of my FW squads survived 3 rounds of combat against the deth kopters before the surviving guy sensibly ran off the table.

Remember, wound allocation shenanigans work for vehicles protected by KFFs, allowed him to save most of the penetrating hits against his kans and all but 1 of the pens against the battle wagon (immobilised in my turn 1 shooting, fixed in his turn 1 shooting).

I believe your post is a strong case for the death of warfish in 5e...

It's annoying when around 36 str5 shots aren't enough. But it really, just isn't.

Also, darn. Was hoping ork boyz were T3. Oh well. I knew the nobz weren't, at least. I coulda sword some horde army besides IG was T3... Was it Tyrannids? Or am I just misremembering?

Some Tyrannid stuff is t3. Ork boyz are str3 however. Maybe you got confused?

That would almost certainly explain it.

So yeah, apparently there's a Str8 Blast-shaped hole in the Tau weaponry...

The failsafe detonator? Armor saves allowed though.

Man, there's a giant 'Instant Death-dealing' hole in the Tau armory, period. Yes, railguns, but most other armies can spam long-ranged S8 weapons (krak missiles, psybolt-autocannons, lances, lascannon, Battle Cannon, etc.) in higher numbers, on a wider amount of platforms, many of which are more survivable thanks to being in units with relatively cheap models or transports. It's a particularly brutal comparison given that XV8s are expensive two-wound models who are easily one-shotted, while ten guardians with an EML, or a half-Tactical with a lascannon, or a full Strike Squad with two psybolt Psycannons in a Rhino are as tough to remove as they are deadly to the vast majority of T4-or-less models in the game.