Minor Power: Every 10 seconds, allies within 15 yards gain a shield that absorbs 1890 damage, stacking up to 14178
(rank 1, on 440 ilvl)
Rank 2: Absorption can stack up to 20% higher.
You could triple the effect and I still wouldn’t use it. You would have to charge the shield for 80 seconds to get it to full power, but after all that, it would still be so weak that it would break from one tick of a random dot.
If the concern is multiple healers stacking it in a raid, then why not just increase the effect in non-raid groups. The Holy Priest’s Divine Hymn is balanced the same way.