Autarchs are generally terrible unless you're playing a jetbike all reserve KP denial list. Farseers with doom, fortune, maybe guide buff your entire army and aren't too bad in CC. I understand the reaper choice with crons and marines. I've tried to make scorpions work because i love the fluff and models but they're not a great option either. No fleet, no solutions against armor aside from one kit on the autarch... If you have the models take harlequins over them. They're faster, more survivable when fortuned, and can wreck almost any unit in the game of comparable before it gets a chance to strike.
Upgrade rangers to pathfinders For the 2+ save.
If you're taking that DA exarch you should take defend so they'll be a true tarpit unit.
D-cannon. Never used this myself because you have much better options in heavy support and it's one of the most fragile units in the game. Combined with it being heavy and 24" range means youll likely never get the chance to fire it.
Wraithlord looks good, but remember you CAN take two flamers. Not twin-linked.
You're list is fluffy which is nice, so if the campaign isn't going to be too competitive you should do whatever you want
but if people are going to be playing primarily to win you may be in trouble with this list.
I've won two planetary empire games with Eldar at my FLGS (both leagues had about 8 people playing) so I know what I'm talking about
Helps to know local meta though. Can you give us any insight on that?
Also if you know how to play the game and strategize, as Eldar you have a huge leg up on people who just whip out their 3+ armor save army and run at you with their "dudesmen."
Good luck in the campaign and keep us posted! I'd like to help out a fellow craftworlder