You just have to adopt a slightly different strategy, its a good thing, it means the game won't be the exact same thing every time (think of jungle patterns and dragon control on SR... its the same thing over and over). That's one thing I really hated about SR... with everything fixed and the same each time, it was much less weighted towards rewarding combat skills than it was just pure knowledge. A game based on pure knowledge gets boring. This is a video game, not chess. I'm not saying LoL is a pure knowledge based game but it depends a lot on it, whereas Dominion is going to be very favorable for those who can fight and position well, as well as think quickly instead of plan every action 10-15 minutes ahead of time. Items will be more about how the game is going in the moment (this will have to be true if the games are as short as they say they are), and less about what you want to have 40 minutes later.
Keep in mind the map is really small so its not like SR where you have to run across the map and it takes ages. Also, what really matters is how much the quests are worth. In smash bros the items can easily have a tremendous massive impact on the game. In that case they are "worth" quite a lot, and it overrides the skill component.
Again, as with all updates, you really have to wait and see. I personally think this is going to be an awesome update.