There are a few exotics I think are worth it for the perks. Basically IB for the infinite ammo and Gjallahorn for the Wolfpack rounds (possibly Truth for the aggressive tracking). I've had many others, Plan C, Red Death, TLW, Super Good Advice, Multi-tool and some others I can't recall off the top of my head. Never used any of them much. I did grind most of them just for the sake of having them maxed but once we found out we were going to have to redo that every three months I gave up! Basically I will regrind my IB and Gjallahorn (if I ever get it) but I haven't bothered re-grinding the rest. Some I've kept as they were (Truth, Mult-tool) the rest I scraped for the exotic shards. I did buy dragons breath and grind it but only because I'm still lacking in the Gjallahorn department. If I wasn't then I wouldn't have bothered. There are often posts on the forums about nerfing IB and in particular Gjallahorn, personally I think they should be making all exotics that good either with perks or increased damage so every exotic should be significantly better than the legendary stuff you can buy at the vendor. That's PvE though. Don't really play PvP. I believe some of the others like TLW are well regarded in PvP.