Played ranked and got obliterated for like 7-8 matches.... but after I figured out the proper strategies, I got up to B-! I don't know if that's actually good, but I'm proud of myself :P
You really have to change your mindset/loadout for this King of the Hill business, the ways you play in regular match will not get you very far. I found that weapons with good range are more effective - more chargers/squelchers and fewer paint rollers. Also, super jumping to your teammates is incredibly important, so equipping stealth jump and having the beacon sub-weapon are very useful. I think the golden rule is not to make an attempt at the point without your teammates - stay a safe distance back and charge your special weapon if you have to. Speaking of which, inkstrike and bubbler seemed to be most effective for me.
Oh and if anyone wants to play, my Nintendo ID is: Overlord_Haze