* Can you do that dungeon with i272? Yeah.
* Will it be harder/longer? Yeah, but it's very doable.
* Did the healer and dps have any right to complain? Nope. First off, from what the OP said they weren't able (or cared) to do some basic mechanics. And instead of doing their job and be done with the dungeon, they started playing even worse and caused more wipes, which is very stupid and hypocritical (it would've been smarter to just leave, if they couldn't play with an i272 tank... on the last boss). They seem to be the typical ones that then go into Crystal Tower or King Mog (assuming that they don't leave if it's on the roulette), for example, and wipe 10 times due to trying to bruteforce everything thinking that gear > all.

None of the levelling dungeons, or any dungeon nowadays (unlike the old non-nerfed dungeons), is that hard to require you to bring super up to date gear in order to complete it. Problem is that some people have gotten too used to overgear easy dungeons, to go crazy with dps without having to care about aggro, to overdps to avoid mechanics that don't backfire when you do so, etc. Of course, that doesn't mean that you can go undergeared when you don't know what's going on in the dungeon, or if you don't know your job/role. But if you know what you're doing? Go ahead.

Truth be told, seeing the amount of handholding that people require nowadays, perhaps they could add an ilvl requirement for levelling dungeons too (other than the obvious pre-requisite of having the required gear to complete the pre-expansion MSQ ones, which must be why the devs didn't put one on the former). I'm pretty sure that people like the OP's healer and dps would find something else to complain about, tho, instead of looking at what they're doing wrong themselves.