"does avoidance give spiky damage?"
"not avoiding" gives spiky damage. when you take 2-5 hits in a row that's when damage is "spiky", and avoiding/not avoiding = RNG. from a healers PoV, i get used to the fights. i get used to the tank. i try to predict when i can throw a bubble or FH on a DPS even when on "tank" heals, and then "get back to the tank".
if you only take two hits as an "avoidance tank" you and I, will most likely be ok. if you take 5, we will probably wipe.
if the tank has "enough" EH, i have a bit more time to "get back to the tank", but what is "enough"?
btw i have a tank with blues that has done everything my healer (ICC10 geared, according to wow heroes) has done.