Fair enough, we saw she could still be hit by commandments, however the fact she just like Mel could end up bypassing the effs of a Commandment like Galan´s commandment is quite a feat honestly.She'd have to catch them first. We saw with Galan that no matter how powerful the mage, if the spells are incapable of reaching the enemy, the mage is done for.
She's pretty powerful, yes, but that doesn't necessarily mean that she'll win no matter what. Perfect Cube is more often used as a defensive technique due to its "trapping" stationary objects. If it's an opponent who can outrun the initiation period of a teleportation technique, they'll have no problem avoiding Perfect Cube. And besides, even if they were caught, it wouldn't result in Merlin's victory, but rather a temporary stalemate.
Merlin has limited magic, despite her abilities' having unlimited duration. Additionally, she cannot, until proven otherwise, use spells which are inherent to other clans, as in the Goddesses' Ark, the Giants' Creation, the Fairies' nature control, and so on.
Meh, if the Commandments are capable of dodging an Omega Ark from two elite angels, Meliodas won't have any issues with a subpar version of it, even if Merlin had her hands on such abilities, which she (very) likely doesn't.
True, but it would give her time to cast another spell, the hax here is that whatever she casts is endless and we know she´s archmage material with how much magics she has showcased so far, Nakaba, hardly even tries to hide it, Merlin as pretty strong, easily best magician, even the commandments cant keep up and I seriously have doubts that the goddesses except for Goddess queen and Demon King actually have spells that far outweight the capacity + added endless duration, of Merlin´s and I say this because well Mera was kinda dissapointing lol

She´s Belialin´s daughter and the commandments pissed themselves up when they found out, there´s nothing else currently known about Merlin´s spell capacity, aside from she being able to cast a lot of spells lol and it wouldnt be past her to be able to use ark, depending on her lineage, assuming Belialin has goddess ties. Even if she cant do the rest of those kinds of spells, it doesnt seem like she will need them with what she has currently in her arsenal and spells are no joke, in this series, she took out one commandment with one + infinity and Mera could trap Escanor and steal his soul with Dark Cocoon when he was caught off guard, even Mel himself had to be saved by Ban when Mera was about to separate his soul from his body, so Mel and Escanor are definitely not invincible against Spellcasters and much less Merlin, but I do agree any of their losses would depend a lot on the situation at hand.
That wont matter much if she can do things like enchant herself or curse her enemies, so far Merlin showcased to be a proper archmage, she hardly has any competition, Mera still the best conjurer/summoner, but Merlin´s spells are more dangerous lol, limited magic or not, if the spells she casts have a endless Duration Mel and escanor will be at a disadvantage, either they overpower the spells used against them right off the bat or they will have a bad time
Even if she doesnt, a endless duration ark alone would still be doing some decent super eff. on a Demon like Mel, Derriere a high ranked 10 commandment, got damaged by one of those, if Mel or anyother 10 commandment was hit by a omega ark even if by a small amount of time, they would sustain humongous damage. The best way to use the spell though is to surround the user in it, that way is more effective since the Demons have high speed feats they would dodge for the most part.