Cho'gall by GDouchington

Cause the next basic ability used to be cast twice in very quick succession, doubling its effectiveness including mana cost and cooldown.

6 second cooldown

Cause Lightning to strike the target location, dealing 39 (+9 per level) damage to all enemies in the area.

When Multicast, a second Lightning strike occurs right after the first one.

25 mana
4 second cooldown

Ground-targeted ability. Area size would be about how big Tyrande's Lunar Flare is, pretty small.

Leave an enchanted Rune at your current location, becoming active after 2.5 seconds. When an enemy moves over this Rune, it explodes dealing 80 (+20 per level) damage and stunning them for 1 second. Runes last for 30 seconds.

When Multicast, the first Rune explodes immediately and leaves a second Rune at the same location.

40 mana
9 second cooldown

The size of the Rune and its area of effectiveness would be a little bigger than Cho'gall's own collision size. 

Send out a ball of fire in the target direction, blasting the first enemy hit for 56 (+14 per level) damage and knocking them back a very short distance.

When Multicast, a second Fireball follows shortly after the first one.

35 mana
6 second cooldown

Grant yourself and nearby allied Heroes 40% attack speed and 30% movement speed. Lasts 10 seconds.

125 mana
90 second cooldown

What do you mean someone already has Bloodlust? I don't see any other Ogre-mages in the game! If anyone is going to have Bloodlust, it's going to be this guy. Sorry, Rehgar.

Enter an empowered state, increasing the regeneration rate of basic ability cooldowns by 100% and causing enemies who damage you to become Corrupted. Corrupted enemies take 45 (+13 per level) damage per second and the cooldowns of their basic abilities regenerate 50% slower, for 2 seconds. Lasts 10 seconds.

75 mana
80 second cooldown

When enemies attack you repeatedly, the duration of the debuff on them is simply refreshed.
He would essentially turn into his corrupted form that you see in WoW: Cataclysm.