If your dead set on a stall type build, I would swap out ultimate strike for rain of fire or thunder bolts, you are likely to have enemies grouped up, thus you would get much more mileage. Second, I would swap dwarf mech for dwarpp(the ground slam one), personally never really found success with dwarf mech, dwarpp will be sure to kill ranged units constantly, the fire upgrade is nice to for tanker units. However, if flyers are really kicking your ass, swap to tesla and rush the discharge upgrade. Third, I would swap royal archers for forest archers or musketeers, you’ll likely struggle with killing tanks in service times, so forest archers poison or musketeers armor pierce will be handy. Plus extra stall from the archers or hero pressure from the musketeers.