There's only 200 cards in the game and Refess has been given the worst in set 1.
Look at it: defense is useless as every color has ways to counter it because le Beau was so otherwise difficult to handle in set 1 strat. So def kinda sucks. Yet Refess units sacrifice HP, ATK, AGI and/or LV for their DEF. Making their units generally weaker than most others (or at least without the nifty abilities of others).
Healing is too hard in this game (as Grimoire initiative is random and you can't "delay" a unit's turn, such as a unit with a healing effect for when units need healing).
Realizing this, they were given some nice creatures in the latest set. But the latest set's theme is large creatures. So yes, their only viable strat as of this point is large creatures since that's the theme of the current set (hence the set's name "Rise of the Dragon Emperor").
Morning is very hard to run as there are only so-many-morning cards. Seraph is needed in (some) morning decks as a soul card, so that's -1 unit, which can be death. even when she's out, she costs way too much SP, and refess has the worst SP generation aside from Lawtia (pasaran are way too weak and require 2 to get +1, whereas Falkow and Gowen both has requirement 1 SP to get +1). They have powder, but that's also the worst of the 4 SP generation cards (arguably). I mean, 10 HP healing is "ok" in late game, but you want to generate SP early game, where ATK and AGI are more important than 10 extra HP during the pre-combat phase (HP during the pre-combat phase are usually useless given that most units die in one hit in everything but the mid-game...). Falkow has the best early game SP generator, as its bonus doesn't require having a unit in play.
Refess was given a pretty good angel, which adds some SP generation. She can take and even deal out some hits, but she is awfully high level and usually becomes a quick target for too many bad cards. Plus, she is level 3, so still easily hit by return/witch/burning sun/etc...