I’ve discussed warhalk a lot on Reddit.
In my opinion he is quite weak regardless of build path. In high tier ranked play do not pick him. That said he is very fun to play and has quite an interesting and high skill cap kit.
If you play him CP he is not your mid lane. He’s a secondary CP carry similar to Baptiste or Lorelei. In fact from a team comp perspective he’s a worse Baptiste. Play him only in top. Build wise I tend to believe Spellfire, Frostbrurn, Halcyon Chargers, Clockwork, Defense, Broken Myth works best. The best way to use his A/Auto combo is to step a little within his max A range, use it, auto, then A again in general for lane trading. But you have plenty of freedom in how to use his A/B depending on if your are poking, pushing, dodging, chasing, etc. Remember the second use of his B counts as an ability activation, so for maximum damage in a 1v1 or when sieging utilize that. Closing gaps with his A can also be a good idea on rare occasions, but is usually only with the charge to secure a kill.
I don’t have much experience with his WP, but don’t believe it to nearly as good. Warhalk is very energy hungry, so builds feel a little awkward. Sometimes even Spellsword is morning enough. His kiting play style can feel great, but when trying to focus down a target (which your WP carry usually does) it’s an inconvenience. I feel you want a zoning bot lane, pick silvernail. He also doesn’t really have the damage to Ben a true bot lane, with the right ratio buffs I could see him being worth the effort, but right now he just isn’t imo.