Let's redefine "damage taxes"

[Avoidy]

Summoner gets a Party regen and a strong targeted party member regen, I think that more then makes up for magick barrier personally,

No it doesn't, because the Phoenix regen isn't an on-demand heal over time. You get it when you summon Phoenix, which you'd do as soon as it's available because that's how your rotation flows on SMN, not because of outgoing party damage. Magick Barrier is on demand damage mitigation that you can plan for and use whenever you want as long as it's not on CD. A vast majority of the time when I use phoenix, its party heal goes out to a group that's already topped off because phoenix didn't line up with any outgoing party damage and holding phoenix excessively to wait for damage to occur is wildly sub-optimal and pointless. If magicked barrier were like smn regen, you'd be forced to use it the second it came off cd, whether there was damage incoming or not. You would have zero actual agency over when it went out, and most of the time it would accomplish nothing.

This comparison is honestly so inaccurate, and it's what I meant by bad faith arguments earlier. Even disregarding the difference between raw mitigation and healing over time, just the fact that MB can be used on demand makes it so much better.