I’m currently just shy of level 40 and still yet to choose a secondary mastery. So far I’m enjoying the aesthetics and playstyle of Ravenous Earth as my main skill, but I may want to change to another skill if/when I get bored of it.
My strongest character to date is a Death Knight (Necro+Soldier) with Krieg’s set. He has ~20k HP and quite high OA+DA, with a range of debuff skills and circuit breakers, the good stuff.