Summoner mobility is overall pretty good. You have only 1.5sec cast times so you can slidecast after 1 second and move 1.5sec after each cast like Astro now. Summons are pretty flexible so you can rotate your summons based on different phases. Like, use ifrit in the phase where you don't have to do mechanics and save titan for the moving phase. For Garuda I would recommend saving swiftcast for Splitstream. You can yourself choose the order you wanna use certain summons. You just have to use everything in 45 sec before your Bahamut/Phoenix is back up.