Before second class, chilling flame will do its work.
If you have not noticed, many buffers are solo-leveling with chilling flame (and its analogy) by casting it with 100% chance at few mobs at once, and then last hitting them.
This counts as debuff, and deals damage regardless of the health of the enemy.
Add to this unlimited mana because of the leech and you have alot of going on.
At some point after 40+ however, the HP of the monsters cannot be drained completely with a single cast. This cuts down the effeciency of this DOT farming in half...
And much later in the game, the damage you receive make it impossible to solo-aoe farm. (Especially after the buff the monsters received lately)
To sum this up: pre 40 - you will be very strong.
But even at mid levels you will hit a wall. And it will be very very unlikely that you will level up 76+ solo.
I can confirm. Unless for very specific cases, having BD in solo is much more benefitial.
(I am leveling one right now)