Step 1: Stand behind their melee minions
Step 2: Throw RQ at the caster wave.
Step 3: Clear the entire wave with 1 spell.
Obviously you're not doing this while someone is in lane (unless you have health advantage/spell advantage/whatever), but nerfing EXTREMELY fringe cases of Mantra E being useful for clearing waves while giving her stronger shields for her team is definitely worth.
And you keep saying things like "it's important to have good waveclear". She does. Without Mantra E.
Again, you're saying Karma is going to be "gutted" by these changes when I literally have never Mantra E'd to clear a wave mid EVER (aside from pre-rework) and when the Mantra W heal has actually resulted in me not dying maybe 1-2 times. It's so unreliable and risky that most of the time it's better to just kill your opponent anyway.
You're also ignoring things like Karma being able to W monsters (giving her the ability to use her W to sustain in lane) and the Mantra CD changes (making her Mantras more accesible to her as the game goes on). This was, net, a HUGE buff, to both Karma solo lane and Karma support, while changing some things that were (honestly) only useful in fringe cases and, again honestly, only then barely useful at all.