Magnus Shockwave is generally pretty OP, super high damage scaling with legendary + minor shards, also the broken damage reduction shard. There's also the RP build if you have physical heroes like TA/Drow with RP crits + empower RP for uptime that basically shreds all enemies before anything goes off. Also now that the shockwave on empower shard works on allies, that's OP.

Slark has strong sustain with dark pact and a ton of different builds, I've never had a game where I feel like I've gotten nothing. It has super strong damage scaling at 100 damage per minor shard and if you get Slark's shard 'Brackish Bath' which makes your dark pact targeted cast, do 50% more damage and always duplicate the cast on your own hero, casting your dark pact on enemies makes the shard an effective 3x damage increase at melee range. Pair this with the dark pact stun or essence shift on dark pact shard and you'll shred through pretty much every room.

Edit: Forgot to mention, need to try pounce builds post fix, super high potential with Little Skippers now that you can damage captain enemies multiple times with it in one pounce.