I like REX a lot as well. I'm with you on that it is easy enough to understand but values a bit of on the fly coordination over individual handling mechanics without coordination. I like shiva EX but... Other than assigning way marks it is all about can you handle the mechanic and not as much, working as a team.
I'm just more satisfied by the team coordination mechanics, but admittedly these fights are harder to be successful with in DF.
