So if people are going to complain about not drawing the best card all the time, why even have 6 cards? Why not just have 1 card that increases damage?

Having done high-end optimisation in SB on AST, when we didn't get a good card, we just rolled with it. Being able to roll with what you got and make the best of a bad card spread was what differentiated a good AST from a bad one.

Also, if someone really wanted a healer job with no deviation in their damage performance due to RNG whatsoever, well, WHM exists.