What about making it into "more damage = more HP drain".
Mods would affect power (damage/status/crit) and HP drain. So, for example, Serration would add +165 damage but would take, let's say, 90 HP instead of 40 at base.
HP drain/damage ration could be based on numbers or percentages of HP. With 2nd option (percentages) it would be "fair" for all frames... but still frames with many more HP should takes more damage. For example <1K max HP -> 10 dmg, 2k -> 12, 4k -> 15. So whil