Don't be condescending, it only weakens your position because everyone will see you as a d!ck.
Firstly I know about the awkwardness, but that awkwardness solely revolved around her W (the specific issue was that your allies needed to know how to position themselves to use the damage/speed/slow when the beam crossed an enemy/ally) which I have constantly criticized and have said needed a rework. Maybe I should have referred to it sooner so you wouldn't get the idea that I didn't know why she was being reworked but I was lazy so kept to the topic instead of adding extra detail.
Secondly I agree that there were problems with Mantra spamming (once again she was most definitely OP) but the causes were far more nuanced. The big issue is that you only had 2 spells to use Mantra on thus the choices that were supposed to be accompanied by Mantra weren't really there. The fact is that yet another weakness of her W is that the Mantra effect was trash so NO ONE used it meaning you just defaulted to RQ and RE. Maybe Mantra came back up too soon, that's possible, if that's the case just nerf the cooldown, this was no justification for a rework.
Thirdly I don't agree at all on your first heal comment. E got just as much Mantra use as Q did, if anything I used E more. To your second comment about the heal being too strong, maybe it just needed a nerf? Though the argument gets shaky when you consider current Soraka's heals work very similarly now with the increased heal based on how low your ally is.
Fourthly some people like healing and I particularly liked the uniqueness of Karma's heal that required an ulti and was balanced more around in combat use instead of sustain which is what Riot actually prefer in their heals.
Finally i'd say a weak mass shield isn't satisfying because it'll need to stay weak because it does too much. Spells have a power budget and if you cram too much into it such as AoE damage, AoE shield and a Shurelia's then the numbers will need to be low and thus unsatisfying so that it doesn't become OP. Also based on how the spell was made you will NEVER have a situation where all 3 of the spells effects will be used at the same time which makes it feel wasted to me, as if there's no 'right' way to use the spell.
I get that you like new Karma but that doesn't mean my criticisms aren't legitimate. FYI I wanted a Karma rework, as i've said countless times her W was trash and the source of so many of her problems, Riot however went far too far unnecessarily changing a character instead of fixing the outlying issues thus angering the champs playerbase and losing a genuinely unique champion and in turn ending up with a new champion that has its own extensive list of problems.