The people saying that Vent is required for raiding: You're wrong. In fact, you're DEAD wrong.
Intelligence, intuition and preperation is (and will always be) the primary factor for succes.
Specifically, people with disabled senses often find amazing ways to compensate once attuned to their lacking senses. No, that doesn't mean he will perform 100% of how he did before, but even 95% is acceptable, especially if his general level was already above other guildmembers which are still being brought to raid.
The communication requirement for deaf people isn't that harsh if they know the tactics, and in that case, giving the essential info to the deaf guy in text doesn't take long and isn't the slightest bit complicated, so the only excuse for not doing it that way is because you're either amongst the top XX guilds in the world or because you're lazy.
So in short, unless he wasn't any good at WoW to begin with, then:
- The guild was a bunch of douches
- The kick was unnecessary (as was any exclusion of him from raiding)
- Anyone saying the guild was right, is wrong. Period.
And yes, this is by Cataclysm raiding standards as well. Cataclysm raids raised the intelligence requirements for raiding, yes, that still isn't going to matter for people who meet the intelligence requirements.
Of course, all of this could more or less have been alleviated for disabled people even more if Blizzard hadn't thrown a hissyfit over the AVR addon being the idiots that they are sometimes. Fortunatly HudMap still exists, although it's an inferior solution.