Yeah, but if youre building MR you dont really need it, and if youre not building MR its a huge buff. So its a buff pretending to be a nerf, Riots latest trend.
Edit: or it would be except youre lying, it never scaled with magic resist. Its full patch history:
V7.4
Bug Fix: The larger sphere from the passive buff now appears in the appropriate location.
V5.22
Combine cost reduced to Gold 500 from Gold 665.
Total cost reduced to Gold 1300 from Gold 1450.
Attack damage reduced to 20 from 25.
Magic resistance increased to 35 from 30.
Shield strength changed to 110 - 280 (based on level) from 250 at all levels.
V4.20
Magic resistance increased to 30 from 25. (undocumented)
V3.14
Combine cost increased to Gold 590 from Gold 550.
Total cost unchanged.
V1.0.0.152
Combine cost reduced to Gold 550 from Gold 585.
Total cost reduced to Gold 1350 from Gold 1400.
Magic resistance reduced to 25 from 30.
V1.0.0.146
Now displays its cooldown on the item itself rather than with a buff.
V1.0.0.138
Shield duration increased to 5 seconds from 3.
V1.0.0.136
Added to recipe for Maw of Malmortius item Maw of Malmortius.
Recipe changed to Long Sword item Long Sword + Null-Magic Mantle item Null-Magic Mantle + Gold 585 = Gold 1400
Old recipe: Long Sword item Long Sword + Long Sword item Long Sword + Null-Magic Mantle item Null-Magic Mantle + Gold 570 = Gold 1800
Attack damage reduced to 25 from 35.
Shield strength reduced to 250 from 300.
Shield duration reduced to 3 seconds from 4.
V1.0.0.106
Shield refresh time increased to 60 seconds from 45.
V1.0.0.105 Added.
Recipe: Long Sword item Long Sword + Long Sword item Long Sword + Null-Magic Mantle item Null-Magic Mantle + Gold 570 = Gold 1800
Stats: +35 attack damage, +30 magic resistance
Unique passive: If you would take magic damage which would leave you at less than 30% of your maximum health, you gain a shield which absorbs 300 magic damage for 4 seconds. 45 second cooldown.