This part might have issues when making enemies squishier.
Let's pretend that your proposed change goes live. Since that 3.4 is basically a 340% base damage compare to 165%, it would leave the similar issue on why people don't stack PPP and CO: diminishing return.
People will no longer run Serration on weapons with decent CC since if x weapon can crit reliably *look at Blood Rush and Kuva Bramma*, which leave Serration become niche for weapons that can't crit. Because running Serration is no longer optimal for crit weapons, which make going for something like Primed Bane of Grineer be easier or whatever multiplicative opportunity costs still make weapon damage become insane, especially vs nerfed enemies' EHP.
Old case similar happened before with from old CO exist (exponential scaling total damage multiplier) vs. enemies' old EHP scaling in which DE fixed the sheer discrepancy and sure, more loadouts are more viable to longer runs, but effectively it makes the enemy squishier in the end to this day.
Proposed change like this would promote more strict meta build since maybe 2 weeks after it goes live, people would go "WTF r u running both Serration and Vital Sense together on Acceltra? Fkin use a faction mod or firestorm for big KPS".
Good idea to fix discrepancies, but do it in a way that respect build variety and NOT making enemies be squishier than before as DE done so. Of course I don't like bullet sponge either, but there is a fkin problem when a Moa Demolyst of lvl 9999 die in merely 6 seconds solo with a Telos Boltace with Shattering Impact and a primer Kuva Nukor (melees have no downtime of DPS and being AOE and all). God forbids a Tigris Prime ("heavy" hitting shotgun that is narrow-targeted, mid-short range, and cucked by DPS downtime) EVER hope to achieve what melees can do for IMO that is the bigger issue right now.