Admittedly, levelling does seem to slow down past 50, but I always thought it was more of a mentality thing because of the sharp increase in the experience needed to get to the next level. However, 1500xp/hour does sound a tad low. Perhaps it might have to do with being slightly too low levelled to handle the mobs there, or just undesirable PT dynamics.
Mobs don't really take longer to kill... The time for each Exp Chain gets more demanding actually, which means you'd actually have to work even harder. I think it's a challenge, PTs are always happy when they manage a Chain #5 (( and always try to get Chains beyond that, really )).
Bottomline is, if you're worried about experience going to always be 1500xp/hour from hence on... well, don't, because it isn't (( unless by some freak chance you keep getting into bad PTs... but let's hope not ))! So... fret not, and keep trying. o.Ob Good luck!
____________________________ﾟ･:*:･｡☆ Kysha ☆｡･:*:･ﾟ Hume BLM|RDM|BRD|MNK|RNG|NIN
(Windurst) San d'oria Bastok Rank 10
(Knights of the Iron Ram) Wings of Honor ∮∮∮∮
Woodworking 100 Alchemy Bonecraft Clothcraft 60 Smithing Goldsmithing 50+
Apocalypse Nigh::Storms of Fate::Eternal Mercenary/Captain
Current Quest Count: 471