Yep, guardian is the MT of choice, no discussion about it. Other classes can tank of course ... hell, any scout can tank a raid mob with the proper healing...
On the other hand,
if you give other fighters the defensive abilities of the guardian, you have to take a part of their dps / utility away.
What is the consequence ?
Only one guy will maintank anyway, so what can the other fighters do ?
Why should we take them in raids if they cant dps (brawlers, berserkers), save the raid with fd (brawlers), heal their group (paladins, monks), buff dps classes (only real role i found for SK...), buff the other tanks, stiffle the boss (monk).
You know we cant give defensive abilities without taking dps away.
The solution lies, in my opinion, in diversity. SoE has to invent other key roles in raid. That will take time of course.
I'm thinking of pulling, of instant agro for knight (MA role), of more self heal and group for monks so they can become independent in raids (so they can dps without any need of healing, that's great for AE mobs.)...