To answer the question first, I've tried several MMORPG's and they are either mediocre or I am too tired to learn them from start (I don't have enough power to read a million beginner's guide).
Thanks to Vallun, there are more offensive tempest builds with d/f and even d/wh. They are not that good by their own but vs an uncoordinated team they are extremely disrupting in any teamfight. I really don't want to ask for nerfs but aurashare trait gives huge value with shocking aura and magnetic aura. Maybe it should only share 75% of the duration.
CMC said it had a good winrate in plat as well, but ye those are probably wins of DH mains since 1000 BC. Also DH is not bad at all, it's just that lb3 is bad.
Mesmer is only good for portal in ATs (with Discord) Otherwise in ranked rev>mesmer=thief. Why did Anet want mesmer to get a roaming role after years of being a sidenoder, I don't know.
I think 30s-35s cd baseline with 33% of used skills is a good idea. This way, Moa + CS = 94.4s cooldown which is understandable. This way, your small skills like gs2 etc won't affect CS that much.
CMC said DH, tempest and core ranger have very high winrates. To be honest, contrary to popular belief, DH was pretty good except for LB3. IDK what to nerf on it though.
@EremiteAngel.9765 aren't you a WvW roamer? I bet you can handle yourself in 1v1s so going far might help you but otherwise below average players should try to go for the most effective rotations.
It means Unranked and Ranked for your context. Edit: Achievements like "League Engineer - Recruit" etc are RANKED ONLY, but usual "Champion Illusionist, Illusionist" etc are both unranked and ranked.
As long as conquest is a thing, thief will be viable. It might not even be close to meta builds of that time, but it will be viable. But in general, going by experience, guardian is the safest choice.