These are not boostable and take two times longer at the top of the scale than the requirements for 70 or lower. Each of them is a sequel to quests which I have achieved with relative ease at around 70ish stats. Runescape appears to be pushing players into more grinds in certain areas, which I find absurd.
I would rather see skills, such as Dungeoneering, which requires skill (and perhaps a strong team, which I believe is an interesting and powerful concept) and also to see these principles being used to other areas. Agility would make for an enjoyable experience, and much more enjoyable gameplay.
While it wouldn't make the game any simpler however it could increase the time required to complete it. The game is easy enough. It's all about time. If you make it harder, but go faster, you will be able to play better.