Title. You're taking away uniqueness and flexibility that only Karma offers and you're making her simpler and less fun to play as/against. She wasn't a problem, so what's the need to warrant a change?
The only thing she needs is a late-game buff with an increased CDR with her mantra passive, but that's it. Anything too overboard will overbuff/underbuff/completely change her, which is HIGHLY unnecessary.
Coming from a Karma main,
RW damage is usually a better bet than RQ, especially early on in trades. It's very unreliable to RQ unless you've already snared someone. If you're opening a combo and can't wait to get the damage off, RW is a very, very potent. Damage is actually equal to RQ early on. As someone that's been playing her for a few seasons in a semi-competitive environment, I usually find myself using RW early on if I'm actually fighting someone up front. RQ is usually if I'm looking to do a cheeky poke, finishing snipe, or my jungler just jumped on them and CC'd them for a second. Later on in the game, usually RW ends up being used in 1-on-1 duels with high damage carries where I usually find myself starting a fight with them that I somewhat start losing but RW, Zhonya and they usually die to the damage since it ends up being close to 1k once you exceed 600 AP.
I don't specifically like these nerfs/buffs, and considering her RW has a 120% AP ratio, it's clearly the successor for 1v1 trades. If they're removing it, they are removing A HUGE PART OF KARMA'S KIT. The heal is vital to her kit as well. The extended root duration isn't worthwhile because you have literally NO damage besides autos and Q's from there, which you could have done regardless.
I always thought of her Mantra as like "Damage" compared to her "defensive" counterparts, It correlated with her lore, and gave her a sense of uniqueness.
~~I was looking forward towards the prior rework because it provided a bit of a new way to play her, and the healing was INSANE if you had spell vamp/torment, I don't understand why people said it wasn't~~. (Tested on PBE, you need tankiness and it isn't efficient and makes her even more of a niche pick).
With this rework (If It goes live), my favorite AP laner might just have to be shelved. She doesn't need any changes, possibly a small buff to hitbox/allowing the RQ to go through units and explode if it hits a champion. She's fine the way she is, but these changes don't hit her major point (as a mage, she's quite unable to do much late game unless you RQ a squishy with a certain angle, but that's almost impossible to do).
If you're trying to make her a support, try Lulu. Lulu does what she does, but better, besides the burst (coming from a Karma main it hurts to say this).
Please, PLEASE, don't attempt to remove her damage, she lacks any reliable damage as it is. The buffs on the mantra CD and the removed damage on RE are perfectly fine. Even consider the RW having it's improved root duration/increased damage/new utility, but doing 50% of it's usual damage (giving it a 90% ratio rather than it's current 120%). Don't gut out anymore unreliable damage she doesn't have.
If these changes do go through (probably will considering past instances where nothing happened), try Bruiser Karma with Lich.. You'll be able to get the damage you had before (slightly) as the longer root duration will allow you to proc reliable lich banes and survive the onslaught you'll get of trying to hold your W. That heal is so powerful.
TDLR; Karma has unreliable damage as it is, and removing the RW damage removes her mageself by a HUGE amount, considering the RE damage is gone. Making the bonus RW damage 50% rather than completely gutting it and giving it a new utility/dampened PBE ones, would be more beneficial to her play-style. Mantra Passive CDR buffs would also be beneficial as her late game Is extremely lackluster.