Whoever says "snore" to Tricia Helfer must have never seen her on screen, her looks may seem somewhat generic (blonde, tall, thin) but she has more talent, charisma and sensuality than many of the other actresses put together.
I've watched
BSG all the way thru, and she honestly ended up boring me. I think it's because the writers wimped out with her (and with all the Cylons, except Cavil, who they just made cardboard-eeeevil). She should have been a bigoted, genocidal bitch instead of some weepy, whiney wimp. Then at least I could have respected her and she would have been fun to watch, rather than annoying and kind of pathetic.
If Helfer had played nothing but a genocidal bitch all the way through, see, that would be
one-dimensional, cliche and really
BORING. Instead, she's showed complexity and played a range of different personalities: genocidal religious fanatic, seductress, kickass fighter, suicidal traumatized rape victim, loving and guilt-ridden woman, determined rebel and leader of her people (some of her characters have fit one of those descriptions, some of them fit more than one). And she made every one of her characters convincing and easy to differentiate from the others, even when they looked identical. That takes talent.
One thing I do agree with: the writers dropped the ball with Caprica Six in season 4 and parts of season 3, reduced the role of Head Six, and sadly killed Natalie, the best remaining Six. But none of this was in any way Helfer's fault. She still played different Sixes well, kicked ass as Natalie so much that a large portion of fandom adored the character more than any other in BSG even though she was in just a few episodes...and even played well against herself as both Natalie and a completely different, weaker and traumatized Six in "Faith".
I agree that the writers also dropped the ball with the other Cylons in season 4. Leoben is the most glaring example - he was so fascinating and charismatic in the earlier seasons, and then they just made him lame and boring. I know that CKR couldn't be in many episodes, but even when he was available, they just didn't seem to know what to do with him, so they let him stand around doing nothing. And don't get me started on what they did with Boomer throughout seasons 3 and 4.

Of course, Athena, the "good 8" became completely hateful in season 4, but the writers apparently just didn't get it, they kept treating her as a heroine.
My Hottest SF/F Actress List (not in any particular order)
Gillian Anderson
Katee Sackhoff
Summer Glau
Elizabeth Mitchell
Yunjin Kim
Kristen Chenowith
Kristen Bell
Claudia Black
Nana Visitor
Sean Young, circa Blade Runner
That's a really good list, although I don't know who Kristen Chenowith is.
But Elizabeth Mitchell fits your above description of 'snore' much more than Helfer does. She was amazing when her character was written in an interesting way and given great material, as in season 3. In season 3, Juliet was one of my favorite characters. But then they made her into a total wimp and made her boring in the next 2 seasons. She still did the best she could with what she was given. Juliet was still cool, despite little given to do, throughout most of season 5, but the finale especially ruined Juliet and made her into an extremely lame, weak and immature character. She makes life and death decisions about the destiny of the island and the world and all the survivors, based on whether Sawyer glanced at Kate?!
An average fifteen-years old would act more mature than that.