Thoughts on sternguard into C’tan?

Seems good on paper. The captain with +2attck/strgth enhancement + 5 should SGV do 10 wounds on average (80% chance of 8) in melee (finest hour turn) + shooting at rapid fire range on oath target. Thats not bad for 180 points. If is definitely a single shot thing though.

Curious if there is another space marine combo that does more damage per point than that