Its a very cool mechanic. The problem the only dot worth casting is venom of the wild, and the mana cost is prohibitive enough that once you get the swarm pet it's usually just correct to spend all your mana on your swarm pet.
Thats a good point. Improved DOTS would also add in a viable way to spend mana on dps when swarm pets are getting blown up by AEs.
I always thought of BST as a shamanistic warrior, that poisons their target with magic, does DOT, with a good pet, and some moderate meele. They have all that, but between inefficiency, cast times, and just plan terrible damage numbers, the whole DOT thing just doesn't seem to happen.
I also never realized how mana intensive swarm pets are. It makes sense because they add a lot of dps, but it is sort of limiting because unless DOTS are actually more mana efficent than pets, the swarm pet will get used (and if DOTS became MORE efficent, then the swarm pets wouldnt get used at all)
Spells shouldn't just be free, and you should have to pick and choose what you are going to do, but this is a pretty limiting mechanic to me.
If it were up to me, I would reduce swarm pet mana to like 300, and reduce the number of pets from 9 to 6 (33% less damage with less lag/space).
Pets are still very nice, but this would leave mana for the BST to do DOT damage.