Am I correct in thinking that with all crit dmg related boosts and using a weapon with high crit dmg, Hollow Point ammo is always the best option, even against 20+ DT targets?

Using Medicine Stick as an example, with Better Crits, and Cowboy against 20 DT target, Sneak Attack, Head Shot, Very Hard:

Hollow Point:
(78 + (78 * 1.5) - 20 * 3) * 2 * 2 * 1.75 * 0.5 * 1.25 = 590 DAM

SWC hand load:
(78 + (78 * 1.5) - (20-6)) * 2 * 2 * 1.2 * 0.5 * 1.25 = 543 DAM

Is my math correct?
And if it is, anyone good at math can tell me where the dropoff point is, how high DT must a target have for HP not to be worth it (or how low dmg/crit dmg must a weapon have)?
Is there even any enemies with more than 20 DT?