Why does Clemency get interrupted? And why does Sword/Shield Oath reset combo?

[Launched]

When switching stances as a WAR :
+ You convert your stacks
+ You don't lose a GCD
+ You don't spend MP/TP
+ You don't break your current combo
- You don't instantly get Defiance's HP when switching from DPS to tanking stance

-Less healing received from any healing ability/spell except Benediction compared to PLD/DRK
-Locked into Defiance for 10s, PLD/DRK can drop Shield Oath/Grit instantly after a tankbuster (PLD can reactivate Sword Oath after finishing its current combo with no Oath)
-Have to sacrifice a Fell Cleave and +10% crit for Inner Beast
-Inner Beast won't heal you to full unless you're full STR, you're using Berserk AND you get a crit so you still need healer help or you need to blow ANOTHER cooldown
-Can't even use Inner Beast outside of Defiance, PLD/DRK get access to all their cooldowns besides Blood Weapon
-WAR has the biggest conflict between using abilities offensively and defensively so either you're losing DPS or mitigation (IB vs FC, stacks from Berserk/Vengeance/Raw Intuition)

You forgot the part where, since heals and shields snapshot, you retain the benefit of buffed HoTs and shields when switching back to Deliverance compared to Grit/Sh.Oath. Very nitpicky I know, but it adds up pretty nicely over time, especially with Conval.
Completely agree with your post regardless.

That also works the other way around: any WAR tanking in Deliverance needs to have Regen recast on them to get the full benefit when they change to Defiance.