Short answer: Yes, druids are the worst tank heals. Paladins do it better, shamans do it better (I used to play resto shaman until ToC came around), and Discipline priests do it better.

Long answer:

Coming from my endgame 10-man raiding perspective, I think druids heal tanks fine. They’re not the best; when I’m in a paladin/priest [myself] combo, I can use my Holy spec without a sweat, knowing the paladin has the tank’s back and I can focus exclusively on the raid. When I’m in a druid/priest combo, however, which happens much more frequently in my current guild, it’s more like, “Oh, you’re Holy? Well, okay. Druid, can you tank heal, and Johannah can just keep an eye on the tank?” My druid buddy and I play a 50/50 role almost, where she’s in charge of the long term heals and I handle any kind of strange spiking. Because my Grid is also set up for my horde (I know, I should use unique Grids for each toon, but I don’t), I see her Rejuvenations popping up everywhere all the time, and I know those people don’t need a Renew.

I guess it helps if you’re tank healing with a raid healer that is aware of your weaknesses! And strengths, of course. Your Swiftmend and Nature’s Swiftness obviously are awesome tank healing tools.

Coming from my level 76 horde perspective, I about had a seizure when I started doing instances. It’s not that I couldn’t do it, but I’ve grown a crutch to priest tank heal abilities that are, well, faster. I’ve got to tell you, us priests have it made in comparison. I’ve been told Nourish transforms the class, but I still have to pay attention when I heal on my druid and I can read a book when I heal on my priest.

I would love to find one that tracks absorption.