Considering that they couldn't even fix Bumblebee's voice box & their limited resources spark storage doesn't seem like a viable option to me.
I may be wrong, but weren't the Dinobots on the ship they needed to travel across the world? Freeing them onboard may not have been the best course of action if they were
Prime does ask for their help first though "so, today you stand with us, or you stand against me."
Grimlock decided to stand against Prime and once Jungle Law was applied and Optimus Prime proved that he was the Alpha Male, Grimlock and the other Dinobots fell in line. Happens in nature every day of the week
That's what we want though, isn't it? we want to see Prime develop as a character. we want to see how he feels and reacts. He's witnessed his family get torn apart, blown up, melted, betrayed by humans and we still expect him to do cartwheels?
If i see one more Prime sacrifice himself or die only to come back i'm going to headbutt something -it's cliche, it's tired, it's old. it loses it's edge when you've seen the same thing for the last 30 freaking years.
rule #1 you must die and come back to life
rule #2 you must sacrifice yourself at any given opportunity
yawn.