Greater Impact

Should you want to know, then this one adds a rather bright blue glow.

Difference between Impact/Greater Impact and Savagery

Some people get confused about the difference between these two. In the end Savagery is better than both of them by 3 dps.

Greater Impact ( +7 weapon damage )

On a slow two-hander, lets say High Warlord's Claymore (http://www.wowhead.com/?item=28293) , Greater Impact makes the weapon damage become 275 - 410. At 3.60 speed, that equates to 95.1 dps. 95.1 - 93.2 = 1.9 dps gained.

Impact ( +5 weapon damage )

Obviously, this is even less than Greater Impact. Using the same weapon, it increases dps to 94.6, a gain of 1.4 dps.

Savagery ( +70 attack power )

Using the same weapon, Savagery gives us (70/14) dps or 5dps. That's 5 dps regardless of what weapon is used.

Either way, Savagery is always better. Even on a higher dps weapon like Gladiator's Greatsword, Greater Impact still only gives 2 dps. In fact, weapon speed would have to be 1.4 or below to even reach a 5dps gain from Greater Impact.

That's because your spell animation quality is set to the lowest in your video settings When max'ed it glow continously rather bright blue