I think WHM are in a very good space. They're more about timing, but at least they have a couple abilities to deal with the situation.

AST could use just a little tweak on Essential Dignity. Reducing the cooldown to 30 seconds and increasing the base potency by 100 will actually make it feel like I'm not just throwing in an extra Benefic II sometimes. Light speed is great - but has a decently long CD and the abilities aren't even truly instant. Yes, there's global cooldown, but casting Aspected Helios, it'll still have a cast bar because LS reduces cast time by 2.5 seconds. I don't count Benefic II proc because that's reliant on spamming Benefic.

The sheer healing power behind the WHM - HoT's, couple of reasonable CD abilities - more than make up for their limited instant cast heals. People really underestimate the WHM HoT throughput.