Simple, there is absolutely no reason ramming should one shot you, no matter the situation, I don't care if someone is going 50 mph or 200 mph and rams me, it should one shot me. This isn't a roleplay server, it doesn't have to be realistic like that.
Also: people currently can just keep ramming you from close distance until you die (3-4 hits) and you can do nothing about it because it takes longer to get up than for them to ram you again.
A suitable solution would be to greatly reduce ram damage or even, in my personal opinion, nullify it; make it zero and remove ram damage because it's not fair.