I promise that I have an actual non-WoW related post coming one of these days. Overdue for a short anime or book review. I like how all of my posts are either when: I am eating lunch at work, right before I go to bed, or at 2pm. One huge ass trick to making just about every instance smoother is crowd control. Especially important in heroic instances where you can't realistically tank more than one mob at a time (depending on the mob and instance I suppose).
The raid icons make it stupid easy to let individual party members know exactly what spell needs to be applied on what mob. Make sure to define the icons clearly before the run starts and to use them consistently. Only the party/raid leader or promoted raid members are able to use the icons. The icons can be applied on both friendly and unfriendly targets. I think the targeting icons are unbound by default so you will need to hit escape, go into the key-binding options and bind them to a set of unused keys. Otherwise, you can just use the WoW API to make a macro:
[code]/script SetRaidTargetIcon("target", x);[/code]
Where 'x' is a number that corresponds to the following symbols:
0 = Clear
1 = Star
2 = Circle
3 = Diamond
4 = Triangle
5 = Moon
6 = Square
7 = X
Most people for example, denote the skull as "DPS this target." Make sure to change the DPS icon mid fight so your party members know which target to focus on.