User blog comment:Telaruhn/Aldric, The Elder Guardian/@comment-4773210-20140409044820/@comment-3974211-20140410023051

The issue with giving a champion with a health shield a defensive steroid is that it bonus resists invisibly increase the power of the shield - since the more armor and magic resistance you have, the more effective health the shield is worth. I know it's no different to just buying resistances but... *shrugs* I'm just paraphrasing spiel that I've heard some Riot guy say about why they won't give a health shield to X or why they can't just give bonus defenses to Y. To the best of my knowledge, the closest thing to a shield AND defensive steroid on the same champion is Sion.

Just spitballing, Aldric's next ability will shield all allied champions hit for 40 + (10 * level) +. This cannot happen again for seconds. (Optional): Aldric must hit at least one other ally to trigger Guardial's Seal.