I don't really mind a strong Raid, clearly not. Neither do I mind something that's so hard you'll need great gear and a good teamplay to get trhough.
The thing I can't support is the existing of "deadweight classes". Gear aside, you should be able to play anything with the character of your choice. Problem is, the Raid is so hard that Raid Groups - and let's be honest, random queue doesn't cut it for this Raid - are most likely to only accept the classes that work best against the boss. Even if the "deadweight class" character has good gear, if they're more likely to die and or do less samage, most groups won't take them along because they would want good runs, and also quick runs when they're farming.
It creates an unnecessary wall between players. I can see people getting frustrated over their beloved main character having a hard time finding a group because well... it's just that character or class they like that's not THAT good for the Raid. Especially since a lot of people don't have time to farm x characters/classes and most of all great gear for all characters. You're most likely to have the best gear on your main. If you have only 1 or 2 characters with gear good enough for the Raid, and those are considered deadweight, then what?
Long story short, the Raid should be playable for every character and every class with good gear. The class preferation should be minimized - I'm aware that you can't REMOVE it, but you can at least work on MINIMIZING it.
That aside, as far as I know the raid is part of the Story quests. Mind you, we'll be getting the whole Demon Realm next. Do they plan on making all future Dungeons as difficult as the Raid? The Raid as a challenge is okay, but there should be a Story Mode type of thing for the player who don't want to or can't do the challenge. Heck, I never played El Tower defense in normal mode because I simplay don't want to. I personally play the game for the story and the gameplay, not because I want to grind a gazillion hours or challenge myself. It's supposed to be relaxing for me. If you're forced to do something that's supposed to be a challenge for high gear players just to continue playing the game's storyline, I think that's a flaw.