I've been using Spriter for the majority of my 2D animations and importing them into Unity as sprite sheets. However, I want to have some really large bosses and animation sequences later in the game so I'll need to have bone based animations in the game to keep the texture memory footprint down.
I've been testing Spine and Dragonbones Pro. Both seem to be pretty robust and have a lot of features. They also have APIs to get into Unity. Spine's base level is pretty affordable but it's Pro level is pretty spendy. Dragonbones on the other hand is free but I haven't had 100% success getting everything working in Unity yet.
I think I will also look at some of the internal animation tools Unity and 3rd parties provide before I settle on a workflow for the rest of the game.