The Blood Ember clickies are great mana savers, and are better than Greenmist in terms of utility. Stacking the procs on Epic and Greenmist is not worth it unless you get the extremely lucky scenario where both proc within 6 seconds of each other.
Troll is the better option between the two regen races due to being able to use Blood Ember. Obviously if you really like Iksar and want to play one, go for it. You won't be screwed. You will just have more down time due to medding while soloing 45+.
Blood Ember Greaves are also useful outside of just mana saving. Having a free FD can save you in any situation where you don't have enough mana to FD. Before level 60 Blood Ember Greaves are your only method of FDing multiple times in a row after a failure, due to the standard FD having a fairly long refresh timer. When you hit level 60 you get Death's Peace, which is a fast refresh FD with increased chance of success. But it does cost 120 mana instead of 60, so the pants are still good at saving mana whenever you don't need to cast it.
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