Well in the video linked below, Luke straight up says that "roles are organic", so there can't be complex mechanics, because Bungie can't account for, say, a specific Hunter Bladedancer grenade to do
something to the 3rd Void-type minion that spawns when the boss touches the 4 golden bells, otherwise it'll attatch to the tank and blow up, leaving the rest of the group defenceless.
That scenario can't happen because there might be only 6 Titans, and Bungie has to account for that. When you add flexibility ("organic") you need to remove complexity. He also says "Nope, all of your jobs is to shoot guys!".
I'm not saying Raids are super easy, just that mechanics wise they'll be simple compared to WoW/Wildstar raids. And that a matchmaking system that calculates your stats and groups you up with people with similar stats would be a good option. Better than nada.
I'd argue this type of matchmaking is
way better than looking at forums. Not only is it a time saver, but it groups you with the right people. It's very likely that you join forum "friends" because you like or know them, but they may be way behind you in stats and/or not play that well, but you still invite them because you don't want to be rude or excluded. For example 6 guys planned to raid and formed a steam group or whatever, but then 1 gets way ahead and 2 of them are occupied with something else - if you switch someone out everyone will be pissed. With matchmaking if you got ahead, you play with other randoms that got ahead, with no remorse or consequences.
Giving an option > not doing so. The only valid thing I've read is the "possibility of nerfing raids if casuals play and get beaten/frustrated in matchmaking" argument. First of all, people will complain regardless, and secondly, like it was metioned before, Bungie's stance could be NOT to nerf raids regardless of complaints. It's their design decision, but acessability shouldn't be affected by that. Keep the Raids untouched, but let people play them without elitist, annoying, unreasonable requirements.
https://www.youtube.com/watch?v=oFRQlCX3Ygs