I usually win when I manage to destroy one of the towers and then can use the slow down of the enemy to outdamage him while the route of my flanking tean that destroys the towers gets them right into damaging the second tower and after that finish the enemy off.
I had some succes with the Rhino and the steelballs doing so it need to be a fast unit. And you need it to do b4 the oponent builds an inpenetrable fortress.
In the end it is about bringing you firepower to most fruition while managing to impair the enemy firepower and unit based shields pretty much never be the solution in the late game, they may work midgame, lategame they are gone in 1 hit.
Some units albeit are strong enough to become really durable so that the self heal meachnism via damage to heal conversion or field repair is valueable and some of the random cards can make a unit outright op for the given game.
Melting Points can be insane that way and totally ruin your game – alos the Overlord has the ability to apply this photonic shield that halves the incoming damage for 16 seconds on all freindly units in a 1oo range.
There is no hard meta so far I have come yet, it is all about towers, counters, doing things at the right moment and the spacing of units.
Man, how often do I lose bcs my spacing of unist is not good enough and some go to early into the fight and some to late and it cirpples my firepower.
Hope it will give you some ideas to work with!