Taking chewie and threepio and r2 to relic 7 worth it?

R2D2 is a waste unless you are going for JML. Chew and 3bac are easily top tier characters in the game as they are great in a variety of teams.

Relic level gains on R2D2 have a pretty low return on investment. He only gives a small percentage of each R level out to other characters and his damage output isn't worth mentioning at any relic level. The team effectiveness of R3 R2D2 is about the same as R7. Due to the damage output of Chew and 3bac, both are worth upgrading to R7.