Ye, now I see that you've mentioned the MS in this other thread. Definitely agreed on that, MS also offers a lot of indirect dmg mitigation translating into a sort of "proactive" shielding. A regular shield is kinda passive, or a brawns way. One does not need much effort to mitigate dmg with it.
@ Dady977: Low scaling is imo expectable as none of the other guys can cast it on cca. all allies in a blink of eye during teamfights ( needs more time and accuracy; and as you said is actually arguably even more powerful..). Multiply the scaling by 5 and you get some ugly values. As TAGDavid mentioned before, the issue (if there is any) could really lie within the fact how much power the empowered abilities bear.