Honestly, this sounds very dramatic over the smallest things (I mean, you really get plenty of opportunity to cast protect even if the tank runs off in the first few moments) and very controlling. If I was tanking a dungeon and the healer gave me that "do what I say or I let you die" ultimatum, I'd probably leave the party on the spot.

Oh and speaking of enjoyment and learning (or what little you can really learn from your average dungeon in this game), big pulls are better. It's pretty much the only time you'll have a use for all those healing and tanking buffs as well as making both roles more active. If I'm tanking a run and I see that the healer isn't casting that much heals and I'm not really using any defensive cooldowns, I take that as a sign that I need to pull more stuff, but maybe that's just me.