I haven’t tried fighting these guys yet.  I’ve been building up my tortoise, monkey, and kirin instead.  Sadly, I accidently replaced my original tortoise that I’d raised from 1 star to 5 stars with one of the 2 stars from the event jungle so I had to relevel him.  Just finished doing that last night when he mutated into a giant tortoise at 5 stars so now I’ll need to do yet another one. 😀