What happens if you just ignore the portals? A while back it was the weekly on my realm, and I 5 boxed it (me tank, 3 ele & 1 resto shaman) together with a disc priest and a mage, and we just nuked it. I didn't go into the portals for sure, and as far as i can recall the mage & priest didn't do that either. I may add that we are fairly well geared (tank, 1 ele and mage icc 25 man (264), priest & resto icc 10m (251) and 2 ele toc 25m geared (245))

Not entirely sure though about my claim. I'll ask tomorrow.