There seems a lot of new monsters with lots of great new skills. Question, is it worth me investing in these new monsters or should I stick to the older ones which I have at levels 120 and get these to 130. I don't won't to spend loads on the game as I don't have it so I can't do both. Level 100 just are too weak in pvp.

@gazza high runes seem to be more of an advantage than high levels

@gazza it depends very much on the monster. Most Warmasters are quite useful at Lvl 100 or 105 with the right runes and relics, and can be extremely valuable support for your older Lvl 120s. Some of the newer non-WM monsters can also be useful at lower levels, Cain comes to mind. The vast majority of regular monsters, including most new ones are not really usable at Lvl 100, though!