You can obtain more tricks from old raids. The default Corrosive Vial ability deals with nature damage, but you can get 2 tricks that use fire and shadow damage. To get the fire one, called Flames of Fury, you will need to obtain it from Ragnaros in the Firelands raid. The shadow damage trick, Sinister Shadows, is dropped by Cho'gall in the Bastion of Twilight raid. On the healing side, your default Healing Vial is a nature spell. You can unlock a holy version, Holy Relic, by obtaining it from Entropius in the Sunwell Plateau raid. These additional tricks are not guaranteed to drop from the bosses and are not account bound. Unfortunately, you may have to run the raid a few times to obtain them, and you cannot share them between vulpera on your account. Luckily, getting additional tricks is primarily cosmetic as they all deal the same damage (ignoring slight differences in resistances).