Barnabas is a fairly complex character.
Although he became increasingly guilt-ridden as the show progressed , Barnabas (as a vampire) always retained a dangerous vengeful edge, even in later episodes. Because he was a vampire, he was subject to doing vampiric, evil things. However, early on, he didn't struggle against his evil nature and these are definitely his most classic appearances. Adding the guilt element though, gave the character more longevity and allowed the audience to feel sympathy for the "monster". I agree the guilt thing could get long-winded at times, but it added an interesting dimension to the character. Don't get me wrong though, while the sypathetic vampire angle gave the character more depth, Frid could play dark, evil vengeance like no one else on that series and it was always compelling to watch him in that mode (even though we saw less and less of it as the series went on).
I strongly disagree about Frid not "doing such a great job" as Barnabas. We are discussing his performance nearly forty years later! Jonathan Frid's performance as Barnabas is classic, despite the occasional flubbed line (I'm sure it wasn't easy learning that much dialogue overnight). He's right up there with Karloff, Lugosi, Cushing and all the other horror icons IMO. Frid absolutely inherited their mantle.
~Penny Dreadul~