So here is a list of situations I have found what to use at what times. These mainly excell in 1v1 and small skirmishes but are also are helpful in zerg stand offs and on keep walls. I do have a few questions on some abilities, hopefully some people know can answer those. I have found that in alot of situations blocking is more efficient than dodging because a timed block will take hardly any stamina and minimal damage (even with a bow)
NB : Teleport Strike, for half a second you can see them charge up this ability, as well as if you pan your camera and see a NB chasing you. You can block this without facing them and take minimal damage.
Siphon and Cripple are spells that you can see coming for a split second towards you, these must be dodged.
Death Stroke Ultimate, For a split second you see them put both hands up to strike you down, (Full charge they leap in the air) Dodging is best but Block this to avoid very heavy damage.
DK : Fiery grip (chain) block this to avoid being pulled. have to anticipate it
Dark talons, blocking seems to stop the stun but you still take damage, most Dks will do this as soon as they get to you.
Reflective scale, when you see them start glowing with a bubble around them do not use magic based damage on them , only melee.
Stone Fist, looks like a stone coming at you, you have a split second to block and not be knocked down.
Dragon leap Ultimate, probably better to dodge but blocking will avoid most of the damage.
Sorc : Shard this one i am not sure, I swear i have blocked it before but sometimes i have also been knocked down while blocking. So i would suggest dodging this.
Temp: Still not sure yet, please let me know if you can block the Spear attack..
1hand / Shield: Shield charge, anticipate this when you see them running at you from a distance, you do have a split second to see it coming as well. Block to avoid stun and damage.
Shield bash, This may change with patch but right now once they engage you in melee or after shield charge they will spam Shield bash, just hold block and usually they will dump all their staminia,
DW: FLurry, its a duration of many weapon swings (7), once it starts hold block, the last hit is the biggest damage hit so make sure you atleast block that one.