I love casting and that is all I've been doing for just about over a year and I normally do horrible against melee. They seem to have a quick answer for everything.
After looking at the scoreboard and my recount after fight. You will see a few of both melee and casters at the very top in damage and kills.
I believe it all depends on the build and how strong it is. I can do very well as a caster, until I get targeted by melee, they can usually lock me out and kill me fast.
You have to have several gap closers and immediately CC and this is where melee has a huge advantage, you can CC chain much easier, because you don't have to cast.
So basically lots of mobility and CC, with high damage and you should have a much easier time with melee, especially now, melee has had much more leading the scoreboard recently.