Tame currently works on a very small fraction of all the mobs in the game and as a result, it is a lot less useful than it once was and hence it's borderline useless. It still has a very small niche but I could see making a ranger that didn't bother with it at all.

It's been a while since I had a beastmaster but serpentkin is in essence just an additional attack spell, wolfkin calls a wolf to attack your current target but it won't attack any other targets and it won't rescue you. The bear you can call at any time in the wilds and it acts pretty much like any other pet.

Bearcharge depends not only on size but on specialty. I can't recall if Beastmasters have a more or less effective lagging bearcharge relative to other specialties. I do know hunters cannot lag at all with bearcharge regardless of size.

Also, bearcharge, like a lot of other ranger skills, work less well in civilized areas.