Gorefiend would probably be difficult to finish off before he kills all 5.

This is pretty much true with a few important exceptions. A lot of encounters have mechanics where multiple tanks and multiple healers or just a bunch of warm bodies are mandatory, either because of positioning / debuffs / mind control type stuff. Most can be overcome with OP heals, tanking and lots of DPS, but some are pure logistics that don't scale down with gear. Of course, you can always get good luck on the RNG...

Basically, many of the following ones can be done with two strong tanks, 2 or 3 strong healers and a few very situationally aware DPSers. I just think 5-man is a bit of a stretch. Basically with these mechanics in mind, it’s a good idea to find some old-school combat log parses and try to match the DPS and HPS numbers, because the fights were tuned around those numbers and it’s probably a good idea to meet or exceed them. Stamina pools make up for a lot of it, but many of those mechanics simply can’t be steamrolled.

A'lar (platforms), Kael'thas (MCs/Conflag/Toy), Tidewalker (Graves 2-4 at a time), Rage Winterchill (Ice Blocks), Azgalor (Doom), Gorefiend (Constructs), Bloodboil (Acidic Wound/Disorient on tanks), Illidari Council (mostly # of tanks/healers). Sunwell (*cough*).

Good points. We did BT regularly in the day and i think we got by with about 15000 raid dps for bosses. I'm having a hard time remembering the exact number, but I believe we did regular clears with 15000 total raid dps. So, yeah, i agree 5 manning it probably isn't going to happen any time soon, if not due to logistics alone (ie council)