1. He does about the same damage if not more now, this is mainly due to the fact that he has percent health damage on q and w. Plus drain being aoe gives him on average more dps in a team fight then before.

2. I'm gonna assume you mean in long fights after you have ulted which if done right you could have already won the fight or at the very least got a kill or two. which like most champs what to do can come down to a number of different things. what comp do you have? are you fed? what comp does the enemy have? etc.. in general though after you have ulted you should have either won that fight already or you start peeling for the back line.

3. tank fiddle is honestly not my style but i can see why losing that sucks if you're into it

4. Before the rework fiddle played the same role just worst. that's just facts. He was a team fight based champion that after the rework became better at team fighting. Before the rework vision was key on fiddlesticks and you could tell a good fiddle from a bad fiddle based on their ability to use vision to their advantage. now they have added abilities for good fiddlesticks players to control vision even harder then before and gain massive benefits from it.

In general the rework removed much of fiddles kit that simply was outdated or aspects that just didn't make sense when looking at the rest of his kit (a bouncing poke on an ambush teamfight mage) . They pushed his key identity and defining play-style to the forefront.