This is my personal opinion from playing Rift and comparing it to my experiences with other MMO's. This is not a cry for nerf other classes or buff my Warrior, it's specifically targeted at the DESIGN of the War Fronts.
I do believe some balancing needs to be done around healing and certain class burst damage. But I don't think that is the main issue nor am I here to discuss that.
The real reason is simple, all the WF are designed to be played in clusters. This is the biggest nightmare for a melee, anyone else of course too. If you get focus fired by 2-4 people you will die no matter your gear or the heals you are receiving. If the DPS knows how to dish it out you will die, no question ask. Let's take a look at the WF's.
The Black Garden - This WF is all about the Fang and people generally gather around it, not to mention it's a fairly small map.
The Codex - You would think this would make it easier on melee but not really. Especially the Codex capture point which puts melee at a huge disadvantage, and also being the main focus of this WF. The cliffs and narrow choke point where caster/range can nuke you down. On top you can be knocked off by Clerics and other classes. This being the main capture point for most Codex I have done makes it melee unfriendly.
White Fall Steps - Usually when I am PUGing people cluster up and end up meeting in the middle. Zerg vs Zerg, once again melee unfriendly.
Port Scion - I don't think I even need to discuss this one since it's the largest WF out of all. Compareable to AV in WoW, never was melee friendly either.
I have done a lot of thinking on why Rift PvP seems to lack so much compared to other MMOs. I believe this to be the main cause, until it's balanced more around smaller group fights melee will get pwned. I am not saying this is the only one and it would fix everything else. But it seems like people over look this and never talk about it.
Please feel free to share what thoughts you may have on this subject.