The only thing wrong with Ren are his cool downs. This latest ArP buff to S&D is a mere band aid on a missing limb in that it doesn't do anything to solve Ren's real problem.
I play Ren quite often as he the first champ I bought with RP.
I have no idea why folks complain about his passive, as I feel it all averages out damage wise and makes for a bit of 'strategic play' (ultimately, if you can't manage rage or think the best way to play Ren in the laning phase is to wipe out a minion wave and then attack the enemy champs... well... yeah... have fun with that... I learned the hard way too, I guess).
His abilities are kick butt in that they: aid not only in fighting but escaping/baiting/ganking as well, make for awesome and "diversifiaible" combos (which themselves can turn into a form of strategic game play) and an overall awesome player experience. Though the fact that Ren's W stun does seem to stun him (if only because of the animation) is a downer. Making things so that Ren can land his W and then actually get something done after the fact (other than follow through with a cool looking animation of a sweeping Bat'leth) would be a huge buff in and of itself!
Yet his CDR handicap is too much to deal with when it comes to his build, and that is where his true weakness lies, IMHO. If you don't buy CDR items and invest in CDR masteries and/or runes, Ren is useless not only late game, but mid game as well, as he is reduced to little more than a harassment machine. If you do try to get at least a 33% CDR ASAP (and don't rely on the blue buff to maintain that % reduction), you then have to make a choice... less damage or less health. No matter which you choose (and I choose to do less damage), it will affect his late game status.
I'm not a ranked player... I have no Elo score... I don't claim to be good at the game... I've only been playing a few months... flame away.