Adding fangs and hair is fairly pointless unless you have a monitor the size of a wall because you wouldnt even notice 99% of the time. Also, adding new things takes time and takes up space which could be used for more... important things than whether a boss has an extra hair on their head or not.
ANet have made various bosses in EotN bigger than usual and it is a good change. Alot of bosses are bigger than their normal counterparts, but not all obviously. Killing Abbadon (who is pretty big) did not feel epic because he was easy, so how is increasing the size of bosses going to make it more epic? If a boss is 20ft tall and dies in 3 hits, its not epic
.New skills would make it a bit more interesting, maybe add some úber energy denial skill to counter Ursan to stop people crying over it. Maybe make it like: http://guildwars.wikia.com/wiki/Fingers_of_Chaos.
With Ursans currently reaping the whole of Guild Wars, bosses dont have time to talk before they are killed. Talking bosses would take too much time and space (look how many bosses there are) and not everyone has Guild Wars sound on.
The lore is: We are human. We like to be in control. We dont like monsters. We kill them in order to be in control of the area. Nuff said
Sinisterness: They kill things. We kill them. Its a fair life. They cant attack towns without leaving the zone. There are no peasants to kill (except the ones they already kill in certain zones (mainly Kaineng areas)) and they cant steal because if they stole from us we would cry and not play. Then they would have nothing to steal. Oh, you mean from NPCs? They only carry whites.
There is no Z axis, so good luck with your jumping boss. Some bosses fly, some bosses come in on ropes, some even pop out of thin air... thats movement enough for me. On some RPGs, they are just stood there (not even patroling lol).
So basically, no time / need for any of the changes except MAYBE add a monster skill to a few random bosses.