i have done ToT lfr, first normal run so i got the bag from every boss + i used 3 coins, and once with only coins, totally i spent 6 coins and no loot at all. srsly is the droprate on 5% on every boss or what!? it's freakin lfr!
The coins have a low chance of awarding you items, just as it was in the 5.0 raids. On the other hand, a handful of 6 examples is a rather limited sample to draw conclusions on what the droprate is, or how useful the Raid Finder of Throne of Thunder is, particularly for those folks that have been running mostly the 5.0 Raid Finders but nothing else beyond that difficulty.
However, if you're a normal raider, it's likely that, in the long run, Raid Finder won't hold many interesting items for you, since Normal gear has a higher item level (522 as opposed to LFR's 502).