I can safely say that the dwarf arsenal at difficulty 9 is impossible to achieve, at least with r1 Gear. Not sure it's any different with r2, just yet.
I've been at this for at least 3 to 4 hours.
Let me explain,
At wave one, You need a strong front liner. Pretty safe to say that the tankiest of them all is Dwarf Warrior atm. But he won't stand alive long till you finish the waves.
Protected by strong obstacles, machinist would destroy the whole team is you don't have proper heal.
So far, I had 2 ways to keep him alive.. Either associate a soul hunter and cleric, together.n
Or soul hunter alone with a lot of crowd control heroes like Rose Fencer and Vengence Spirit. And you need at least one if you don't to get killed by machinist ultimate.
Now... 1 tank, 1 healer or 2 healers. You'd be sure to timeout if you don't use strong damage dealers. The best out there is Sorceress. Ninja is most of the time out of the question unless you're incredibly lucky on RNG and he doesn't get one shot by a missile (aoe) or lazer (single target). Managed to make him survive.
Managed to get to second wave safely... and here comes the insanely overpowered pilot ... On skill, one shot unless he picks a tank. I can't prevent him to use one skill, even 2, and ninja is on him... but he manages to shoot rf or sorceress or any other squishy hero you might use sooner or later ! we are not even mentioning his ultimate... I'm talking about normal shots.
in other words, you need insanely high damage for second wave with enough cc to prevent him from doing anything.
If you put that much damage, you won't survive the 1 wave.....
Even if you manage to reach the third wave, you'll face both at the same time !
You want to clear wave 1, you'll fail in 2. You want to clear 2, you'll fail in 1. If by miracle, you get passed wave 2, most probably with several dead, you'll get buried in 3
Hope it is solvable at r2 gear... But for now, It is too much. I cleared everything, and it's ridiculous to block on a that feature... :P
It's not a whine, but I think no one will manage this part of the game. If you did, I beg you to share =)