I think the blame for one team dominating for rounds is far more likely to lie at the feet of upkeep and people using crap at x1 and their Holy Avenger's at x5.
If one team has all the cavalry, then the other team is going to have all the archers, or all the pikes, or some class the other team is missing by virtue of having all the cavalry. Those cavalry are easily countered by teamwork. The problem is that cavalry will often ride in a mob, while infantry scatters to the wind and rarely offers coordinated resistance in nearly even numbers.
5 cavalry loses to 2 pikes, a shielder, a 2 hander and an archer if they are looking out for each other.
In reality things work differently. cRPG has a retard percentage of 90%, most people even refuse to listen to suggestions/commands of others as a matter of principle, because they are smart themselves, noone needs to be smart for them, so they don't listen and do what THEY think is best. Which usually is running into the first mob of 5 or more enemy players and then spending the rest of the time in spectator mode. because that's fun for them.
People are unpatient, and they don't think about the game. If you have to attack over an open field, the enemy cavalry will wreak havoc among your team, so if you could simply wait for the enemy cavalry to become unpatient and then taken out by the archers or pikemen, you could advance way safer, but even the small and absolutely logical suggestion of "Don't attack before their cavalry is down" appearently is too much to understand for the average cRPG player. And this is only one example.
If a team is constantly losing, it would be the most logical thing to change the behaviour, as the current behaviour didn't lead to success, but do you think people listen to "Defend the ruins, this way you are safe from their cavalry and archers, and THEY have to charge if they don't want to lose their multiplier in a draw!"? Nah, the players MUST have their own head, and charge straightaway to their 0:4 map result, because they don't need anybody else thinking for them and the [W]-key is so comfortable, it's really difficult to release it.
And yes, I tend to even follow plans I think they are not the best, as I am aware that everyone following a bad plan is still better than everyone following his own plan. Because my self-esteem is so good, I CAN stand the idea of listening to the ideas of someone else over the internet without feeling like being patronized.
I think if the developers would implement some features which support using tactics, and would choose their maps more carefully to grant fair matches, the problems with the unfair distribution of classes between the teams would not be so much of a problem any more.