Thanks!This (any 5 player dungeon) beats the heck out of 4 hour dungeon crawls.
I assume you have tanked Naxx. Would you put it near the top in difficulty? I have not tanked HOL or HOS but if I can handle HTOC, I should be able to handle them on heroic?
H ToC can vary from easy to hard since the first two boss fights are random.
Naxx is not necessarily harder but is more technical to tank. You should go along as DSP to learn the fights before tanking. Tankspot has some great reference videos for tanking Naxx. (Note - Naxx has 4 wings with spider (easiest), plague, military, and construct (hardest))
H HoL is much easier overall then H HoS. I like it though when the daily is H HoS since you can avoid most of the instance and just do the event and final boss. With a good group it should only take 20 - 25 minutes.