KFF is boss. 5+ save, while not great, means 1/3 of your orks don't die. Put him in a squad, in the middle, and all you worry about is Assassins and Mind War.
culler already did the math about how many boys need to be saved for just 1 KFF. With 2, obviously you need to save twice that many boyz. You generally won't take that many cover saves before you hit the enemy lines
Apart from that: Mind War and Assassins are not the only things that can take out the Big Mek. Any ordnance whatsoever, infiltrators, anything with jump-packs/fast transports/deep strike capability. In short, roughly 1/4 the stuff you see fielded against you can take out the KFF-wielding Mek
If the Assassin shoots, you lose him, but who plays assassins?
Anyone playing Inquisition will usually have an assassin (unles they're playing pure GK/pure SoB), and many IG and Marine commanders have taken to using them too.
If you get mind warred, then that is one dead Eldar (either way. It's a total 50/50, as you use LD 10 for the test, just like the far seer. Half the time you'll shrug it off and laugh.) If your KFF goes down, you just pull back if your shootin and charge if your not.
A dead Eldar from what exactly? You probably will be able to charge a seer council if they've mind warred you, but actually killing them is something else entirely. They all strike before you do, they wound your Orks on 2s, and they have 4+ re-rollable inv saves to deflect whatever attacks you manage to get in.
As for shooting them, forget about it - I've seen Seer councils stand up to *vastly* more firepower than an Ork horde can put out
Not to mention that if your Mek gets mindwarred, the units you were hoping to shoot/assault with are likely to be shot up by the rest of the Eldar army
Flamers? You charge them before they get range, or blow them to pieces.
Anything with a transport + flamers. Anything with jump-packs+flamers. Ever heard of a Hellhound? Very nasty tank vs Orks.
And none of those units will be shot or charged as they're easily hidden until the time is right. Not to mention they could easily take out the Mek as well as stripping away the cover save.
CC? Against ork? Are they insane? YOU get the charge, YOU have the power klaw, YOU have 60 boyz.
You don't get the charge vs anything with jump-packs. You don't get the charge vs anything with fast transports. You don't, in short, ever get a charge with infantry apart from vs other infantry. And you certainly don't have 60 Boyz when your opponent comes into flamer/assault range, ignores your cover save, and assault you.
BTW, Boyz are not that good in assault. Shitload of attacks yes, but a *good* CC unit will wipe out the entire killzone if you have your models spread out, or most of the boyz in the killzone if you have them tightly packed. At the end of the day, they're still I2 models with paper maché armour.
They lose. IF they don't come at you, laugh as your lootahs wipe the board of big units while they snipe 18-30 pts of ork a round.
Except that Lootas don't have the range to cover the entire board, can't guarantee hitting a damn thing (rolling 1 shot each at BS2 is nothing to shout about), have crap AP, and of course enemy units are often hidden or at the very least in cover.
Warpheads make better transports, and they can do 30 boyz
'Ere we go?
Now I'm *certain* you're just talking theory rather than actually having tried this.
models? Even with a "hit" on the scatter that unit has a massive footprint to try to squeeze in without losing any models. If they scatter at all, you lose a *lot* of boyz due to the deep striking rules.
Simply Put - A BM w/KFF can
be a nice addition to the army.
But they have a lot of limitations, a few counters, and to get the maximum
use out of Orks you do not
want to go for the pure horde approach. You need Stormboyz/Kommandos/Bikes to take out/tie up key enemy units, otherwise your entire horde will just get picked apart piecemeal.
Big units=big footprints. Big footprints means that small, elite armies can concentrate their force vs small parts of your force and the boys are in the way of each other and cannot fully support each other. Stormboyz, Kommandos, Nob Bikers, Warbosses on Bike, can mitigate this. but it will take away some of those massive numbers.
In all honesty, I can only assume that all the people reporting "big wins" from shooty horde ork armies purely based on shoota mobs/lootas are playing on planet bowling ball vs static armies.
LoS resitrictions, range restrictions, having to move through difficult terrain, and the fact that you simply cannot bring that number of guns to bear on any 1 unit due to Horde unit footprints makes it incredibyl difficult to actually get mass numbers of shots vs mobile armies on well-terrained boards.
Now if people claimed lots of wins by using a few shoota mobs and fast support from stormboyz/kommandos/bike Bosses, I'd believe it. But 150+ Boys with shootas, a KFF, a Warphead, and a loota squad or two is simply not an effective army on a properly terrained board against a good army/good player. As I may have mentioned, I've been having fun using the new Ork codex, but the "shooty horde" just isn't all that good IMO.
In 5th Ed (according the the leaked PDF and rumours), the CC horde becomes much more viable.
No need for the KFF since screening will buy your boys a 4+ cover save anyway for the cost of a Grot unit.
The "run" rule will allow you to close the gap faster.
Killzones are removed, making the Ork's I2 a bit of a non-issue.
At that point, a mass of footsloggers (supported by Stormboys) will start making a large
impact on games rather than just shuffling 6" per turn and getting shot to pieces.
Right now, however, as much as I love the idea of 150+ Orks marching towards the enemy, it just doesn't work too well. The Horde is too vulnerable to fast, hard hitting armies that can take you apart piecemeal.