Resistance Trooper vs Luke

So, I've had Resistance Trooper since the beginning and he has been fantastic. He hits hard, crits a ton and in general has been a key team member. But I figured for long term, I should switch to Luke. They seem to fill similar roles in the team. So I finally unlocked Luke, and ranked him up. But overall, I'm pretty unimpressed with Luke. On the same team, similar level and gear level, Resistance trooper hits about 1.5x to 2x the damage of Luke on both normal and special attacks. I think most of it is that Luke never seems to crit, despite having a +30% chance from his passive skill.

Does anyone have these two characters to compare and have a different perspective?