Good for you, Supermax! 38% melee defense will definately make your tank feel more "tanky" and will work for about every TF except Recluse (he's a bugger for Fire regardless of how you're built without some buffing support). The small drop in healing flames wont matter much, as the improved defense will keep a lot more of that damage from landing in the first place. Enjoy your tank, and dont forget to laugh as your damage numbers pile up compared to other tanks who may have more survivability - it comes at a price. Not only can you tank, but you can legitimately fill a melee damage role as well. 
Yeah it's very nice to be standing next to a stone tank...taking no more damage than he is, while putting out about 10 times more damage
Anyway, I haven't had trouble tanking anything so far other than hamidon, and I think it's pretty much broken anyway, so everybody has trouble with it.
Hamidon is not broken. It is designed to bypass all of your defense and resistances. The only mitigation that works is healing, regeneration, and Essence of Earth inspirations. Knowing the strategy is important too.