So there was an interesting post on EJ and I let it slide off but then Graylo blogged about it and I thought at this point I'd throw in my two cents as well. My issue with recommending the speed enchant [Tuskarr's Vitality] is when you remove [Icewalker] and fall below the hit cap, you are required to regem your sockets to reach the hit cap again using [Veiled Monarch Topaz]. This results in a net loss of stats.

What I'd like to do is take my theoretical druid and change his boot enchant from [Icewalker] to [Tuskarr's Vitality] and swap out one gem to gem for hit. In fairness, it is difficult to model what 8% run speed will do for your DPS, so I will be ignoring the added DPS time on the boss, assuming that it is negligible (at most 8% of the time you are moving). My theoretical druid carries 3k SP, 40% crit and 389 haste. His counterpart carries 2990 SP, 39.73% crit, and 389 haste. If I needed more than 8 hit (either 9, 10, 11, or 12) then I would need two [Veiled Monarch Topaz]. That druid would look like 2980 SP, 39.73% crit, and 389 haste.

I will be comparing straight spell spamming instead of a rotation so that I get a look at the impact to the individual portions of my rotation. I shall name my druids Icewalker, Tuskarr 1 Gem, and Tuskarr 2 Gem. For sake of comparison no idol is equipped.

Icewalker

Tuskarr 1 Gem

Tuskarr 2 Gem

Percent DPS Lost

TL:DR

Every DPS loss was rather minimal (on the scale of .75% to .3% depending on the spell). Were we to weight the percentages of damage done by each spell, I think we would find that for Tuskarr 1 Gem, we tend towards the chosen Eclipse percentage. The real question then becomes, how much more casting time will a player acquire by being able to move 8% faster? Let us assume that we are Tuskarr 1 Gem. Then we would need to find an additional 0.5% of our fight time to be casting.

Let us take a 6 minute fight that forces us to move for 10 seconds ever minute to avoid some fire mechanic. This amounts to 1 full minute of moving. Now, with a speed boost, to escape the mechanic we would only need to move for 9.2 seconds per time. This is 55.2 seconds of movement as opposed to the original 60 seconds of movement. Naturally this allows us 8% more casting time during the movement portion. This amounts to 0.8% more cast time over the course of the entire fight. A DPS increase for Tuskarr 1 Gem and possibly a DPS increase for Tuskarr 2 Gem if an extra spell were able to be cast in the given time.

That kinda failed as a summary since it rambled on a bit so here is TL:DR v2. It seems like the DPS loss from [Icewalker] on a fight that requires movement at least 10% of the time will be less than the casting time gain from [Tuskarr's Vitality] for the replacement of 1 gem. 2 gems will require ~15% movement for this to happen.

Musings

While I agree that such fights exist (General V. etc) I feel that there are many cases where having a speed increase will encourage a player to stand longer to try and get that single cast off. I suppose technically you can squeeze in an extra 8% of your run time as casting if you've got the enchant but that will vary with every movement mechanic and therefore is unreliable. It is therefore my belief that Tuskarr's Vitality promotes laziness and bad habits among raiders, decreasing raid awareness and reducing the emphasis on reaction time even though reaction time will still be a vital component of the raid environment (i.e. spell switching, treants for BL, rebirth, etc). In addition to the aforementioned points, I also want to point out that a good raider is already moving out of the fire, moving onto snow mounds, avoiding shadow crashes, and performing a myriad of other maneuvers already without the speed aide. And if sh!t really hits the fan, there's always catform/sprint. If you need this more than once a fight, you might want to consider why you're reacting so slowly.