It's actually pretty funny, because at some point, I stopped worrying whether my squads could complete a map, but my focus shifted to making sure my squads could complete a map without a single one of them wiping. And after that, it shifted to making sure my squads could complete a map without a single girl wiping (I still don't always manage this one, but usually do).

But, that last one also makes the maps a lot trickier. Before, I could count on the fastest squad not killing the last boss, giving the other squads more time to mop up the rest of the pests. Nowadays, I have to make sure each squad is on the right tent, possibly even use a customized unit for the map, to make sure every pest is cleared before the first squad reaches the pole. Having non-optimal units, where all 4 squads together are strong enough to complete a map, while 1 or 2 of those squads might still wipe against the last boss actually makes this game easier.

tl;dr:
Don't worry too much about being efficient, but when you reach that point where you can take on anything without breaking a sweat, it may become something to fool around with. Anything goes at that point, Trigger squads, AOE squads (rarely mentioned, but very efficient for cleaning up a map!), Speedy Sonic Hedgehog squads, Counter squads, Solar Blast squads. Such squads are very efficient for their purpose, but not always optimal for completing a map.