it just occured to me how useless erebus' last swarm is for how much mana it costs. I never actually use my last skill point on it just because it only does an additional 150 dmg at a cost of an extra 350 mana!?!

i could suggest to drop its mana cost slightly, but i think ive got a better idea.

Why not add a lvl 15 skill in the 'bite' skill line.

Bite lvl15
900 mana
Instant

Steal 775 health and 400 mana from target. Target moves 30% slower and armor is reduced by 850 for 5 secs.

OR

Bite lvl15
900 mana
Instant

Steal 775 health. Your attack speed increases by 25% for 5 secs. Target moves 30% slower and armor is reduced by 1000 for 5 secs.

i would be happier with either one of those, more so than the last lvl of bat swarm.