I find it interesting that you seem to have assumed my players are casters. In fact, this low-power group is one pure mortal (with Guns 4 and stunts), one Red Court Infected (Inhuman Speed and not much else), and one Minor Talent (with The Sight and Psychometry). By comparison, my usual high-power group had one Fire Mage, one Were-bear, one pure mortal gun-nut, and one true believer who mostly supported us with maneuvers and healing (DM let him grant others temporary Inhuman Recovery on a limited basis as "Faith Healing").
Not really an assumption, just covering another possible aspect of low-power play. By "your spellcasters" I simply mean "any spellcasters in the party". Normally, the spellcaster starting a battle with one fate point, next to his comrade pure-mortal's three to five, isn't as big a deal when the caster has a good magical defense. But in shallower water games, I've seen this bite casters because they lack those defenses.
As for your specific group, without a mage or some good grenades, they will have some trouble when outnumbered. Are these the same players as your high power group, or equally savy in terms of declarations, maneuvers, ect?
It could simply be that the tactics that work well in your higher power group, with a completely different group of character types, won't work with the new characters.