It's competitive if your opponent doesn't have tons of direct damage multi-targeting grimiores in their soul card lineup. (Which they almost always do).
Good cards to use are Haste Soldier, Swallow Scout, Wizard Soldier of Regus, Wizard Archer of Regus, Enchanter, and maybe Sylph Sorceress. The trick to this file is having Ex Vordore and Azure Beastmaster in your soul cards. You build up field presence quickly with your low level units which can hopefully handle your opponent's opening units using the edge on agi, and when one of your cards go the remaining ones gain incredible attack/defense/hp/etc buffs which let them steamroll your opponents early game. Of course, one row clearing card can pretty much send your entire strategy down the drain. This strategy would benefit greatly from having a good tank in the front lines, such as Sea Claw or Sea Hunter, but since you spend all of your sp early on setting level 1s and 2s and reviving your easily killable level 1s and 2s the sp to do it just doesn't build up. I tried playing such a file back when the expansion came out and it's not bad, it'll definitely steamroll people using slow openings and mostly single-targeting soul cards, but it can run out of steam very quickly if the opponent is on par with agi or has annoying double or triple targeting soul cards.
It might work better if you somehow get Mage Paladin Distrier out on the field, since your units will buff his attack up and once they die off you can use the sp to put his def through the roof. Renally could also work since she can provide some much-needed lifespan to your front line cards and also knock off units pretty fast herself. Water Dragon could also work well for a late-game unit.