If, and only if we speak alone about a hard hitter, between the ones you mention, as I noticed Tiburtus is costumed, he would be your man.
However, Proteus is great for events, and very good for raid attaks (he is average mana, thus being harder to charge, but so is Tib).
If this is all your roster, beterans advice to first get three 3* of each colour maxed, for staking, and then doing three 4* each colour for the same reason. I did so, even having some 5* to work on, and worked fine for me.
Staking colour could be a great way to improve your raids attaks, and if you can’t decide you could bring the contestands to 3/60 (your staking would improve by a lot) and then choose the one that suits you the most.
For me, the order will be Proteus, Tib, Ridgard, Sabina (because completing events gives you challenge coins, and I like that). But that is my prefference.