The line we tend to throw out there is: "play what you enjoy"
It can't hurt to experiment and try a class you never played on live but if you want one character to level 60, make it a class you know you won't be easily tired of.
I don't know how many retired clerics p99 has but its a lot, based on people just wanting to "play whats in demand"
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Also have a browse in the guild discussion forum. You'll soon be recruited by a leveling guild on your adventures if not
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