Swiftcast may be useful in lv44 story trial, but not essential because it can be passed with only healer + tanker alive. But having a swiftcast will allow to revive a dps (if they die).
Eye4Eye may be useful in lv41 and lv50 dungeons, but not essential - it works like an extra damage mitigation cooldown for tanker, but tanker will not need it unless decides to speedrun (which is a bad idea with new players).
I suggest getting swiftcast after you get to lv50, because some people just get upset when are not revived asap. Most of people will not notice if you don't have eye4eye.