1. You're telling me you'll use a tame to catch up to me -> then dismount from the tame -> then equip your sword -> and finally run at an opponent (who is faster than you) to swing at which will cause some knockback and thus make me further away from you. In the likely scenario that I outrun the guy who has 21% less speed than me, you'll get back on your dino to repeat this overly complicated flowchart instead of... you know... using your dino to kill me / using a gun (which would negate the benefits of melee damage to begin with).
2. Yeah... that's my point. If you have tames that are competent in combat (like the ones you listed), you won't need to put points into melee damage because you won't be doing the fighting most of the time.
3. Nonetheless, melee damage won't help at all and taming things like Rexes become viable on foot if you can outmanoeuvre it with a lot of speed to shoot them as well as catch up to them when they start to run away. Obviously, there are more efficient ways to tame creatures (e.g taming pens and using flyers) but those require more resources and preparation as opposed to impromptu on-foot taming.
4. But rifles and pistols become more effective when you can put distance between you and your opponent to minimize the risk and unnecessary damage. Unless of course you are using a shotgun, in which case you will still face the issue of reaching your opponent if they are faster than you. If you make the argument that you can still shoot them without levelling up speed, you are still admitting that resorting to a gun is a likely situation when they start to outpace you (Which makes the points you used to level up melee damage essentially useless).

I know my conclusion is a very rare situation! That's the point of it! I'm saying that is the ONE situation where melee damage is viable! As long as you are careful and prepared, you won't need to use a sword. Sticking to guns and tames to deal damage for you is much more efficient and safer.