Connor does remind me a bit... but not as much as you think. Actually last night when I was playing doing some liberations Connors voice sounded really close to Altair....
But there is a HUGE difference between Holden and Connor. Connor lost his mother, his village was attack and lost a dear friend. Because he had little and lived off the land to begin with he isn't left with anything mid game except for his anger towards to templars and his primal hunting insticts.
Holden was a brat that hated life and the challenges it brings without realizing he was going nuts very slowly. While the angst and anger are similar they come from two completely different motives and circumstances and result in two different outcomes. Not to mention Holden just swore and got his butt kicked a bunch. Connor gives the beatings and doesn't receive them.
Stand firm for what you believe in, until and unless logic and experience prove you wrong; remember, when the emperor looks naked, the emperor is naked - Daria