I think you misunderstood my post. Back in wow, when raids were still new to many players, before rift and many other mmo's, there was this raid lvl 80 called naxxramas, it wasnt the hardest raid introduced, but it was hard, had difficult mechanics that required every player to participate, meaning each player no matter class had an assignment in each boss, if 1 failed, the raid would wipe.
People complained as usual how difficult the raid was, and that they werent geared enough to clear it. A top guild then stepped in with previous xpansion gear (meaning lvl 70 gear) tottally ungeared for the raid and managed to clear it.
When that did happen, it proved to the whole mmos and skills is more important than gear.
Did that raid have dps checks? Yes as all raids, it had dps check, enrage timer, boss hitting more than the tank could take etc. So how could that guild clear that raid with previous xpac gear?
If you find a raid that is to difficult for you, dont focus on gear, gear is going the easy mode. Instead focus on your skills, learn to play your class to its fullest.
This depends on the fight. If the fight was designed that that is possible...well, then it's possible. If the fight has been written that it requires say 10million raid dps to beat enrage timer, and no matter what, the best dps people can pull on dummy parses (nothing to screw with the numbers) is 8million; then it simply cannot be done without new gear. This is wholly on the dev team that designed the raid.
As i mentioned earlier here: many of the earlier raids had such lockouts, by design, and typically the second boss in the raid. The only other ways people got around that were by exploits, bugs, or taking advantage of soul changes that were quickly deemed in need of further tuning (see: nerfing... got overbuffed).