Samurai weaponskill/ability Higabana vs Kaeshi:Higabana

As a play Samurai there something that irks me. When using you ability to upgrade your samurai attack, it seems to me Higabana gets short end of stick. Both Tenka Goken and Midare setsugekka are able to "effectively" double damage by striking twice with a boost to potency,while Higabana gets overwritten by Kaeshi:Higabana with only a 15 potency boost for dot.

I think either the dot potency should double or they should stack to be effectively 2 strikes. Maybe, I don't understand the math. I'm a big fan of old FFXI support and Damage over time usage and feel its lacking.

I'd also be willing to accept making Kaeshi:Higabana the same potency as Higabana but change it to an area of effect to damage multiple enemies.

You seem to be misunderstanding Tsubame-gaeshi a little bit here. Kaeshi: Higanbana is not a 15 potency boost to Higbanbana, it's literally just Higanbana but with the potency you'd get from using Kaiten. You're not overwriting the DoT, you're refreshing it. Besides, Kaeshi: Higanbana is a waste of a 60s cooldown anyway. It only saves you 2 GCDs, compared to Kaeshi: Goken saving you 4 GCDs and Kaeshi: Setsugekka saving you 8 GCDs.