Hey OP, that's a pretty well thought out trade. It seems like Vancouver gets good value, and Oilers most certainly do.
I don't think it's completely out to lunch for the Leafs, but I don't think it gets the deal done either. If Tanev didn't have an injury history, there wouldn't be much hesitation, but unfortunately he does.... let's say he goes down for long stretches... then the haul looks like Yam, and two thirds... kind of an ouch. I'd rather have two pieces of high quality, than two thirds and Yam.
Send Vancouver's 3rd to Edmonton, keep Yam, keep your third, send Dobson to Toronto instead. That would be my counter.
Reworked
Receives:
William Nylander,
Van 2019 3rd, Tor 2019 3rd
Receives:
EDM 2019 1st (top 5 protected, otherwise becomes 2020 unprotected 1st + 2nd),
Andrej Sekera (cap)
Receives:
Chris Tanev, Evan Bouchard