I have Jolly BD Azu as the listed variant for this core just because I'm personally a big fan of Jolly BD Azumarill, and I think it works really nicely to lure and weaken Mega Venusaur, which can really pave the way for Breloom in the lategame. BD Azu is also nice on this core ...
The rest is in Special Defense with a Careful nature because it can help to take threats like Zard Y in a really nice way. Mega Scizor has the classic BO spread: 248 HP and 16 in Defense let it take 2 Earthquakes from max Attack Adamant Landorus, so that it can easily set up on ...
But you're right there, Mega Gallade can somewhat handle Gengar, and definitely handle Venusaur. In the mean time, I'll try and think of a good third partner for this core. Thanks for the attention on my cores btw Bludz, it actually means quite a bit to know that my cores are ...