Yes, Skill caps, skill/stat/hp decay are the real solutions to the issue.
However, with decay you would not be what you are today. At least it is not supposed to be possible.
If after they turn on skill/stat/hp decay and make the skill pools works correctly you still can have high enough HP to take little to no damage from even high level players, many will feel that the system is either broken or being abused some how.
Either way, all this will lead to lots of pissed off player and I feel sure they will move on to other games.
In a game like othello, its experience and knowledge that allows a player to win against another.
Here, atm it is more about HP than anything else. Contests where a single player always wins the rewards, even against 10 other contestants simply because that player has vastly higher HP than any other contestant, does not prove that players skill or ability... its moot he is going to win.
Truly, what is the point of participating in such a "contest" when the outcome is a given?
Its game mechanics that are to blame here. If you want to try and have the highest HP in game that should be strictly up to a player to reach it. Yes you have worked hard for this. And yes others could have devoted them selves to the same man hours you have... in theory.
In practice that's not realistic. Most of us don't sit at our computers playing games for a living like you do. Not your fault, but also should not give you an advantage IF others cannot spend the same amount of time. It's about balancing.
Balance is very important in almost any game played. You don't pit a grand master against a new player in chess do you? The reason is obvious. It is unfair. Unfair to both actually... no challenge to the grand master and a waste of time to the new player as they really wont learn anything from the experience.
The same thing applies here. With no caps, no decay there is NO chance a new player can stand against a player like you. And it surely should not be a stroke to your ego to defeat a player not equal to you, unless you are a bully at heart.
I would think that you would want a challenge not the easy button.