You can actually do pretty well in LoL if you are good at DotA, the only real problem is that you have no idea what each hero/item, but the rest is quite easy, something similar should happen on the opposite case (LoL to DotA), not quite the same since DotA is way more complex than League, but some of the basics are the same. IIRC Dendi switched to LoL back then and got like #3 on ladder in a month or so.