a little napkin math on the thunderers puts them at about a 25% damage loss compared to index without khemist, and a 30% damage loss if you factor in the khemists lost buff as well, which has them now (if they remain costed similarly to what they currently are) at well over 30 points per point of damage. unbuffed naked liberators are around 20 ppd, so they are about 50% worse damage for the points as liberators. skywardens, depending on weather they get to shoot or not, are around 10-13ppd, so roughly 3x the damage output for the same points as thunderers.

astoundingly pillow fisted. among the worst damaging units in the game barring wizard bonks