I understood Holtz need for vengeance more. He lost his family as an adult. To go out into the world, suffer hardships, fight the good fight, but then fall in love, marry, have children, to have something innocent and warm that gave him a reason to know being a demon hunter was worth it and to have a safe haven from the violence, only for it all to be taken away and being left with nothing. He had no reason to live and became a shell of his former self. Angel raped Holtz's wife, murdered her, and turned his daughter into a soulless demon and forced Holtz to have to kill her, and then he bragged to Holtz about how tasty their blood was ("especially the little one") and about how he raped Holtz's wife ("You're wife, she kept repeating *saying Bible verses* on us, of course, I repeated on her *raped* a few times myself"). It was made so much worse by the fact that it seemed like Angel and Darla (she happily assisted with the torture, massacre) were still a couple and that they got to have a child.
Wood was four years old when he lost his mother. I felt like he was more upset over losing the things he thought he would have had if she had lived. That he didn't sign on to be raised without a mother.
I did have a lot of sympathy for Robin until he found out it was Spike that killed his mother. You could tell that it changed the way he saw Buffy and when the seal brought out his rage he called her a filthy whore for having been involved with Spike. He tried to undermine her position as the leader/General that can make tough decisions and think of the mission first. I loved when she said "it's the mission that matters" since he got Giles to help him with his personal vendetta by acting as if it were all about the mission when it wasn't and because that statement is something that Niki would say. Buffy didn't just go into the Room With Wall to Wall Crosses and threaten to let Spike kill him if he ever attempted to murder Spike again. She first told him about how she lost her own mother, said she understood why he did what he did, reminded him of the war with the FE (remember she did have a vision of thousands of Turak-Hans in Hell on their way up to slaughter them all) and that they would need Spike (the second best fighter) if they were going to survive, etc.
No, Buffy should NOT have more time for personal vendettas. She forgave Willow, Spike, Andrew, Faith, and Anya for their crimes and would not have let someone plot to murder them while they were under her roof and "reformed". The morale in that house was really bad already with Annabelle taking off and getting killed, Chloe hanging herself in one of the bedrooms, the FE posing as a slain Potential "Eve" and trying to get them to not trust Buffy, posing as Joyce to get Dawn to not trust Buffy, Willow afraid all year to do serious magicks thinking it'll turn her into a homicidal killer (its why Buffy said that she was the most powerful one in the room because Will wasn't using the power that she had), Spike not wanting to even kill demons until what Buffy said to him in GID, etc.