Bossing for lvls post bb

So I'm trying to decide whether to make a new build or keep the one I'm working with now (for the most part) after bb for a couple of my chars. Is bossing for levels still a viable option? I read a lot of the bosses I fight now get some pretty nasty nerfs exp wise. I guess my question is am I better off going for the mobby skills and grinding or can I use my 1v1 techs and lvl by bossing?

And also can we still get those reverse db masks in gach? I wish to obtain