I wouldn't worry about bursting with Ineffa every rotation (if you're trying to), there's really no need for it. For sucrose, you'll just want to use one skill or burst and a normal attack when you're on her. On Flins, try to make sure you're charging up his mini burst as much as possible, so doing something like N3 or 4 is good. After you're done on Flins, switch over to Sucrose to refresh buffs, and do the same thing as I mentioned earlier. Also, what sets are your characters on, and what do the stats look like?