My more detailed impressions after taking a closer look:
Rune Knight:
Thematically fine, sound mythological basis (and we have had similar things in earlier editions). Why Fighter? We already have two "magic fighters". This theme could fit a barbarian, cleric, bard, or artificer. In particular, I think this would make a better "magic barbarian" than the exploding flumphs guy (did we ever find out what they where smoking?).
The rune powers themselves seem a bit over-complicated. I would rather have something straightforward like adds +1d6 fire damage to your attacks. The appeal of 5e is it's simplicity compared to other editions.
Otherwise I quite like it.
Swarmkeeper:
I like the idea. Why fey? I don't see any reason this concept couldn't work with actual tiny beasts (e.g. bees).
Powers: Why does the swarm do force damage? Poison or piecing would seem to fit the theme better (even if mechanically weaker). Why can't I send my swarm out to attack on it's own (i.e. a pet)?
A disappointment.
The Revived:
WHY A ROGUE?!!! Even more than flumph-arian this seems to disrespect the core class. I spend two levels sneaking around stealing stuff and stabbing people in the back, then I hit level 3 and all of a sudden transform into a pseudo-undead thing? A sorcerer would be a better fit for the concept.
Powers: Bolt from the Grave's connection to Cunning Action is weird. It's a bonus action, but in order to use it I'm
required to dash, dodge or hide?! It's almost like the designer is thinking Cunning Action is a limited resource. Otherwise, it's interesting, since it allows the rogue to wield a weapon that isn't eligible for sneak attack without gimping themselves.