In my opinion:
You need good technique to execute tactics effectively
You dont need good tactics to have good technique
Technique is more important as it is an enabler that allows you to not only have good technique itself, but allows you to execute a more diverse range of tactic.
Good technique also can act as a block to prevent other teams from using their tactics - e.g. someone who has excellent technique at holding a lane, can put a block on the baddies tactic to gain a bit of real estate; it then comes down to the baddies technique, to enable them to execute their tactic effectively, as they try to take control of the lane.
The above model is very simple - and once you start to enter more than 2 players into it I think it falls apart a bit, but I think it conveys the jist of it
Technique>Tactic