Ok, a few things here.
1) You can still use colossus slayer and Hunters mark together. Just want to clarify, because you were comparing them for some reason. Don't rule out Hoard Breaker either though, because that's potentially a higher metric of damage, but it relies on you being surrounded, which isn't as common.
2) Objectively, Half-Elves are far superior to Humans in terms of build potential. With point-buy being your only option, you'll only ever need to utilize +1 across two stats, which is exactly what Half-elves provide. Plus the other plethora of features, like a cantrip and darkvision.
3) Beast tamer (IE Find familar) is fun at early levels (like 1-2) but around level 4 the low damage output isn't worth using. Comparatively, resistance to fire is something that is EXTREMELY useful across all levels.
4) Ensnaring Strike uses your spell save DC, not athletics. The section about "creatures you restrain having a hard time escaping" is misleading because currently there is no Grapple action in the game. That's planned later. Bounty Hunter still might be worth taking, but only for Investigation. I personally recommend Keeper of the Veil as Arcana is used quite often, and Prot. from good and evil is a very useful spell in certain encounters.