As a fiddle main I only play support and some mid for the last two season.
He is strong support because of fear and poke. Then his ult can make up for your bad mid liner that has not damage late game.
His issues
Lane - Farm really sucks. The crow bounce change means he is force to use AA or drain to get farm. He spells are mana heavy.
Jungle - just remove him from jungle. Doesn't clear quick enough and needs too much mana. There is a reason only AD and tank junglers are strong. Sure he still can jungle just balance his around mid and support would be easier.
Support - think he is in a ok spot atm.
General - Drain mana issues. Only ticks two or three times on average not the 5 times it is budgeted for. The mobility creep and all the stuns make drain and ult an issue. All the shield stop drain healing effects. The addition on new rune direct nerf to fiddle.
Fixes.
"q" is changed to "Fear me" comsumes all endless fear charges. Target gain a greaves smokescreen effect for .50 per charge. Target is also fear for .25 secs per charge. Targets within 150 units are feared for and extra .50 sec. This will allow fiddle to have a close fear for dives but also stop the flash fear for a good cc.
Add effect on "e". Minions hit with crow are marked for 5 secs. Any damage done to them by fiddle procs 10 + (20% ap) magic damage. This would help is farming without more damage to champs
Drain is now a tether that you can moved with. Damage is reduced 1/3 to 1/2 Mana cost adjusted to reflex this. Just update the kits to be more mobility but also reduce the standing drain tanking.
Ult can now but cast on an ally. If cast on an ally the damage is reduced by 50% and mana cost are increased by 50%. When cast fiddle can select ally or himself. 1.5 sec cast time. If cast on self fiddle "ult" wont start until he click when direction to jump at. If cast on Ally it just swarms over ally no jumping evolved.
Passive changed to Haunting the night
damaging enemies cause them to get a stack of endless fear. -5% MR per stack stacks 5 times. Fiddle gains 2% movement speed toward Endless fear enemies.
Just some ideas on an update