He is not OP, although he is pretty good throughout all the levels. So, you should get it and level him up, even though he is in epic arena (lvl60), so it will take a while without luck. When you reach orange he will still be good, although not as "OP" as in purple levels. Awakenings will make him fade away from main arena and only be epic arena material.
Hell no! Lumos is an amazing hero for normal arena at end game. I think people give too much credit to awakenings. The best teams you can get are not comprised of 5 awakened heroes.
Well, having 5 awakened heroes as defense would be madness. Zem is almost a must, but I mean... you can pretty much defeat someone with or without a Lumos. He is great, but in my server is starting to lose its prime, and we are still in O/O1. Lumos would be excellent if he would have some +1/2/3 abilities as default. But with all the glitches (he doesn't stunned everytime under X level) is getting replaced by others. If his ability were constant he will be awesome still. But I hate that sometimes interrupts and others don't. He is a big gamble.