I hate using Legendary myself now. Been trying to work on a competitive team. I can make the 5IV easily now myself (though it's now a perfect 31, the IV checker just says outstanding in all 5 or 6.

I still find it hard figuring out which mega to use. Mawile seems to work great for me, especially running with its egg moves. Other than that it might be Kanghaskan instead. Other than that I haven't got a full team running yet. Nothing but trials with teams and items. Still have a lot more to test, but it still takes time to breed the perfect Iva and then EV train.