Originally Posted by Buster Wolf

At what point should one stop doing 2-1 for farming and go for stage 11+ based on their team (I stopped at 8-2 since I heard it's a big spike in difficulty)?

You want to stop doing 2-1 when all the silver and bronze in your squad are evolved and at around level 20-30, at that point the gold efficiency will strike back at you. Gold units can be raised to evolution point too, but it might be difficult to do the jump from 50 to 60 with just lvl 20 manyus.