Bleak watcher is affected by grenade buffs and deals stasis grenade damage and inflicts slow and it does it fast enough to freeze freeze being one of the best debuffs in the game.
Child of the old gods deals void damage slows and weakens and additionally based of your rift you either get health or ability recharge and on kills of affected enemies you get ability energy back.
Arc soul deals arc damage can be given to teammates and slightly speeds up rift reacharge when teammates are near
I did not mention in the starting bit but this is where my opinion comes in as a bottom tree arc pseudo main as I never really had the ability to main it in pve due to its lack of viability in pve anyways back to the point. Arc soul sucks compared to its stasis and void counter parts it is pathetic when it comes to high end add clear and awkward when it comes to build crafting this should not have been a problem in arc 3.0 but it still is and the solution is simple arc soul should have gotten a debuff if it got be it jolt or blind it would be fine as that would give the player leverage for builds and provide a much needed utility for storm callers kit and it would strengthen the support aspect for teammates too as both debuffs would makes the adds spend less time shooting team mate this would be perfect.
PS I have tested this solution in a very convoluted way so I can confirm arc soul would be excellent with jolt