Summoner's utility is battle rez, eye for an eye and virus but that doesn't justify them having the lowest DPS because Scholar and White Mage have priority when it comes to using those abilities if a Summoner has to rez in a FCOB progression party it's a wipe.
SE is balancing the Summoner against other DPS which is a mistake since Summoner is DoT it has to be balanced against the content or it will be useless. There is a reason modern MMORPGS don't have a DoT DPS it's the same reason why they no longer make controllers because MMORPGS have a faster pace and content is designed differently so DoT abilities are spread across Direct Damage Dealers just like Crowd Control is. In order to make the Summoner viable SE would have to dumb down content or make the Summoner 3-5 % stronger than other DPS.