IMO the difference is definitely noticeable, literally some minutes ago I was in a Halatali as ARC with a PGL and it was clear that they were single-targeting only because threat was skewed and it was just... Weird? AoE play is core to dungeons, so it's unfathomable why at least 1 ability isn't available the moment we unlock them. 45 is ridiculously late for healers to get AoE, BTW. Also, it's funny to play RDM in something like Sastasha, where to get White Mana you have to single target and it's all so lopsided.