"Half-Blood" lacking

("Half-Blood Prince spoiler alert)
After my marathon session to finish the "The Half-Blood Prince," I was sort of disappointed with it. It didn't have the same ferocity that "The Goblet of Fire" and "Order of the Phoenix" had sustained throughout.
These books had action going on at different levels, with various minor climaxes occurring here and there. This one, I found, really only had one, and that's when Snape performed the spell that killed Dumbledore. So that happens and then the book continues for two more chapters, which is fine except it went on a little too long.
Several things about that, too. I am a Snape fan. I have always been under the impression that Snape is not evil or bad, only misunderstood and with a little attitude against Potter. So if he's bad, then why didn't Dumbledore see it, being that he's all-mighty? To me, if he couldn't see through Snape's facade, then it diminishes Dumbledore's greatness. If Snape is not in league with Voldemort, then why did he kill Dumbledore and then run off? How will he explain his actions to Harry and the wizarding world without being judged as a killer?
But I am resigned that Snape could be evil and was using Dumbledore If so, then there should be a showdown with him and Potter, as well as with Voldemort and Potter. Or will book 7 finish and Snape be left alive and perhaps ascend to the status of Voldemort after V. dies at the hands of Potter.
I must admit that I was disappointed that Snape did what he did. It leaves me feeling odd and out of sorts. I do not mind that Dumbledore is dead, since it leaves only Harry as the one who has the ability to kill V.
An interesting scenario would be if V. kills Potter and the wizarding world is in peril. But I think that's highly unlikely.
I also expected some other minors characters to die. I would not have minded if a few "unknown" students bit it and maybe a few death-eaters, as well.
I did like that Malfoy was more human and had emotions. I don't think he would have killed Dumbledore if the others hadn't arrived.
And what of Snape being the Half-blood prince? That was kind of cool. For a good portion of the book, I thought it might be V.'s book.
There was also too much "hooking-up" in the book. It seems that by the time it was over, everyone had his or her partner (although Harry did the valiant thing and departed from poor Ginny). Still, there was quite an abundance of love going on, maybe a little too much, since it seems that love is what V. is incapable of dealing with.
Oh well, I'll still be anxiously awaiting the final book to see how it all turns out in the end.