PvP Tamers are Overpowered....
Many "stakeholders," of which I'm one, are going to argue your base premise emotionally. I won't, in fact, "tamers are overpowered" is about as intellectually undebatable as anything could possibly be, once you shelve the emotions of it all. It creeps into everything dev does, note that almost every new aspect of the game must include an "anti-pet" mechanism simply to provide challenge. Beyond your base premise however, I think your recommendations go overboard:
There's so many angles to this discussion so I'll just throw something out there. I really think tamer should be required to have Vet skill. This could be implemented by having pet Stat/Skill decay over time (as the pet is neglected health care by it's owner)
Also, I think as time passes pets should eventually become weak and die. Maybe after 1 RL week the pet starts to go. Also I think to stable the more powerful pets such as the overpowered Greater Dragon it should cost at least 1 Mil maybe 5 Mil per week to stable it.
Vet is a great skill, depending on tasks to be performed. 2 of my 3 tamers use it, it's indespensible to how they're played. As a requirement however, the "logic" doesn't flow for me. "Herding," one of the never used skills, might fit as an additional requirement for obeying commands and/ or loyalty checks. As templates get rather crowded as is, and with new skills on the way, were herding to be included in checks, the weight/influence/ requirement should remain reasonably low. It becomes a balancing act for dev, as it also needs to have significance for higher level level creatures. Taming difficulty could probably be lowered overall, going back to an original but since voided pledge that powerscrolls would never be required for play, and dampening much of the argument reference item based skill modifiers. The trouble is, as your thread title implies, that a couple hundred poinits of skill, coupled with a cu or greater dragon are disproportionally strong relative to skill point investment.
I couldn't disagree more with your decay proposal, it shows taming isn't "your thing." Try taming a blaze cu, the spawn chance of which are 1 in over 23,000. At 5 minutes time invested per tame, accounting for other spawn and paragons in the spawn region, and have it go "poof." After a design requirement of 2000 man hours - oh no. Seriously, no way. Increasing the gold investment to stable also assumes that everyone plays 24/7, and plays to attain gold, neither of which is true for the majority of players.
So, I agree with your premise, just not your "solution."
Edit: Before it becomes an issue, let me cover some "history" regarding my thoughts on herding, as I've voiced them before over the years here and on other boards. As above, I do think it should play a role in obeying and possibly loyalty checks, scaled based on creature level. I also hate "nerfs," and am strongly opposed to anything infringing on anyone's gaming entertainment/ enjoyment. As inherently such a change does "take away," I feel it equally important it "give something back." I've recommended before that for every 10 points of skill, you add an additional stable slot. At one point I also recommended that for every 20 points, it add a "follower slot." As to the latter, my original recommendation would need a revision, as 2 greater dragons would be a tad too powerful. 1 added follower per 25 would negate scroll effects, probably not a good thing, and 1 slot per 30 points would cause a scroll requirement for 2 cus, the scroll requirement probably also not a good thing.