Shirrak is a nightmare, he's the only boss I've not managed to beat at the right level through the whole of TBC and WOTLK so far (at 73 now). I tried lots of different strategies but with ele shamans as dps I just couldn't do it. I ended up going back at 70 and downing him with fire eles and shocks.

Ikiss however is pretty straight forward. Have everyone follow your tank throughout so you are all bunched on the boss and tank him by one of the pillars, as soon as he emotes and starts casting run around the other side of the pillar. You have plenty of time to do this, I usually had a second to wait before the spell went off. Return to him, rinse, repeat. You'll have to deal with the aoe explosion he does straight after but this is fairly light damage. Only other thing to do is keep dispelling polymorph to keep your dps up.