I've always had DC with corner abilities just because it is fun to have a Leighton Baines in my team and have a DC be a top assist provider. Btw, playmakers make good setpiece takers as well.

DC with corner abilities will work if their attacking points are high enough.

Generally, just having a SA tied to a player doesnt mean it will work as SAs are supposed to compliment existing skill points. It is a secondary consideration, not the main consideration for a player.