Cobalt is the hardest to deal with on any setup. U should aim to get the boss down before the enrage, forgot how long it is but if ur not getting it down within 9minutes or so tell ur dps to kick it up a notch.
Jasper,jade,ameth is the easiest combo by far as the raid dmg is tiny.
If ur stuck with Jasper,ameth,cobalt it can be tricky with breaking the chains on Jasper petrify.
Its all about awareness and ur dps as ur healers will be focusing mainly on tank and chain dmg and if ur taking avoidable dmg which most of it is, slap them
Good luck peeps! U will get it!!