Why should Chimera be terrible? Skullshield + Afla-stall your enemy, play Graveyard + Eclipse, use Plague, enjoy 23 4/3 Skeletons combined in one big Chimera. You could BB one or two Skeletons before doing that and you get a 92/109 Chimera with Momentum and Gravity Pull.
Its not that chimera should be terrible, it is terrible. I've yet to see a successful PvP deck using chimera. For the combo you suggested to work, you need heavy death quanta, darkness quanta, gravity quanta, and earth quanta. This makes the deck a quad deck; quad decks are highly inneffective and the deck would be pretty slow running as a rainbow. It takes a good deal of time to set up a chimera. In that time, any number of superfast decks will win before this deck even sets up. Chimera has the disadvantage of beening a very slow card to pull off in a game were speed is paramount.
I say all of this about chimera to show that its existance is in no way a buff to guard. Until a better card comes out to put a premium on hp, there is not really much to do other than drop the cost to 1
that will make guard effective.