The hero is just dogshit above Herald because there's too many things that can just shut him down.
It's game losing when 20k networth just disappears because they got on-top of him.
So I suggest a new shard.
Sniper mounts an allied hero. When doing so he cannot cast spells and loses his passive "take aim". However he cannot be targetted until the allied hero dies and will sit on-top of the allied hero shooting off his shoulder.
Lasts 5-10 seconds depending on balance.
45 sec CD, once per fight used as an escape when someone jumps him if he has a tanky offlaner to mount.
It would work similarly to naix's ulti. With just an icon showing to everyone on the mounted hero. But should just give him a cheap build in reliable answer to getting jumped.