I assume they didn't change the Tiger drop rates, just made Roc better, but I wouldn't worry much about it if I were you. I've been playing since around when Destiny came out, I've done countless strikes, and I've only seen a single Exotic weapon drop from either Tiger or Roc. I'd see a legendary once every couple of weeks or so in tiger, it wasn't very likely. Just get the DLC and play on Roc, it's got fairly good legendary drop rates. The raids, nightfall and Xur are the best way to get exotics.