Harrow is more focused on damage dealing than he is on healing and energy regen. The only reason people compare him to Trinity--Just like with Oberon--is because he has a support component to him. He's more an offensive support than Trinity's dedicated healer.
1 is just a solid CC wave that gives you Overshield, 2 drains those shields into a crazy reload/firerate/heal buff, 3 generates energy pretty easily, and 4 gives immunity followed by an additive critical chance buff. What's interesting, though, is that his 2 and 4 are driven by affinity range rather than power range. This means that they have a base range of 50m, unmodded! That additive buff gets really stupid, especially with sortie level damage.
Trinity will forever be the god mother of healing, but that's because DE put in an ultra unbalanced healer as their first support Warframe. She had to do the job that no other Warframe could at the time, and so has the kit that she does. At least she doesn't have old, literal god mode healing like she used to.
If you're having trouble with headshots, at least the Scourge's thrown mechanic will help with that. Honestly it's not that difficult unless you're fighting infested units.
