Ever since I left WoW over four years ago, I’ve played MMOs exclusively on laptops, and every laptop I’ve chosen has run the games I play on medium settings just fine. Sometimes I play with a cooling pad, other times I don’t. As long as you don’t smother the computer while playing, or cover the exhaust ports, normally you’ll be fine.
Now, I’m currently using an Asus K53S model laptop with:
i7 (2630 QM) processor
NVIDIA Geforce GT540M graphics card.
6gb RAM
600gb HDD
I’ve had this thing for a couple of years now, and it can run TERA, Rift, FF14, and GW2 all around medium settings. I’m not picky about super high fps as long as there’s no lag, so avg of 25-30 fps with these specs is perfect for me. I got this model for no more than $450 on ebay. Check ebay, and look forlaptop models with generation 3 or 4 i7 processors. Then from there, look at laptops that have HD4000, NVIDIA, of ATI graphics cards, and you’ll be fine. (my wife plays on a HP laptop with a HD4000 graphics card and i5 processor, and she runs low settings perfectly fine)
All in all, if you wanna play on a laptop, there are ways to play on a laptop. Don’t let anyone tell you otherwise 