First of, every spell at the start of icbt2 was able to get interrupted. And even way before that.
This not a sudden oddball change out of nowhere, if you paid attention you’d understand that’s just how spells work in this game.
Nor does it make sadhu2 or possession worthless.
While sadhu 2 arguably isn’t in such a good spot, neither are majority of (cleric) classes. And by no way is sadhu2 the worst of the bunch. At least it can hit enemies, unlike most druid transformations.
Not to mention clerics have plenty of ways to prevent damage, all it means you get to spam it slightly less.
For a 20s cd skill with good dmg and a immobilize, yeah i do expect a pretty strong downside.
It’s also not the first “bug” that made possession stronger then it should be. Nor will it be the last as long as it’s still in beta.
And your reasoning for the “problem” is beyond stupid. Knockback =/ damage.