I think the core problem lies in content scaling, here's why :
All content have a required minimum ilvl to enter. This requirement is supposed to be the lowest ilvl you need to clear that particular content. On top of that, we all know that main stats trump everything (Except your weapon) when it comes to stat scaling.
So, basically, as a DRG, if you enter a content like Susano EX, you're supposed to have 300 ilvl worth of STR.
Now, if we look at tanks, it's completely different. Their "main stat" is supposed to be VIT, if we take into account that it's the only primay stat on accessories that they can "need".
If a tank wears a full i320 left side and all STR accessories, he only have 196ilvl worth of Vitality.
It's just complete nonsense that someone can clear a content with such a low "main stat".