[@Alamantus]
Frequently, it does come down to GM input, when I didn't think of something. That's true of every game, though. You can't play an hour of any tabletop game without the GM having to decide if something the party did works or not because the game designer didn't think of it.

Okay, so I'm going to use a single example. Something very basic. Somebody is trying to evade getting stabbed by your halberd. Which they tend to do. It looks simple at first. If your attack is equal to or higher than their evasion and you're close enough, you stab them. If their evasion is higher they evade it, if you aren't close enough you can't reach (and shouldn't be trying in the first place). However, there's actually a lot of depth here.

So, what if your attack is lower, and you can't hit them? Then what? Well, obviously you need to raise your attack or lower their evasion. Raising your attack can be done in a number of ways. The simplest is to aim, which makes the attack take more action points but also raises your attack massively. But there's other options. You could change weapons, use something that's either smaller or is of a different weapon type with better attack. If your halberd isn't hitting, both a knife and a spear might have a better chance. You might also try shedding some weight, since encumbrance penalizes attack (amongst other things). 

The other option is to lower their evasion. The simplest way is to change attack types, and use something harder to sidestep. If you switch from thrusting to swinging, you'll face half the evasion and be much more likely to score a hit. Sure, swings are (usually) less lethal and (usually) more hindered by armour than thrusts, but they're a LOT easier to hit with. Otherwise, you could try having your mate help, because evasion has a limit on the number of people it can defend against per round, and that starts at 1, so if you and your mate both attack, one of you can't be evaded. Or, you could chase them into a place where they can't move as easily. Evasion is lower on slopes or stairs, and it's lower if up against a wall and especially in a confined space. This also helps keep theme in you reach, too. Attacking by surprise would also help, because by default evasion only kicks in *after* somebody has taken their first turn, and if you attack by surprise you go first in the first round regardless of initiative. You might also try attacking them from behind, as evasion doesn't work on enemies behind you by default. Lastly, attacking during their turn also works, since people don't get evasion during their own turns, and this can be done as a reaction to their actions, which is a whole other system for another time. (Basically, I'm talking about what D&D calls "attacks of opportunity", though they work differently here.)

On the other side, what if an enemy is trying to hit you and their attack is higher than your evasion? Well, if you would rather not be stabbed, then you can try moving away from them. Reactionary actions here can include movement, so moving backwards as much as is allowed will force them to either follow and take an attack penalty for movement and possibly miss, or stay still and almost certainly not be in reach anymore anyway. Another option is to move into a place where they simply can't use their attack, like going into a narrow corridor or between a pair of trees or something if they're trying to swing. Alternately, get behind something. You can also try hitting them first, if their attack is big enough to allow a reactionary action of that size, in an attempt to impair their attack. And another easy one, you can just get closer. You might try stepping inside their minimum range, so their swing or thrust can't connect. They'll try to move away, though, so this doesn't always work very well and should be reserved for enemies with a long minimum range you are already close to. Grappling is also an option, though that takes just as long as attacking, as if it works it gets you very close to the enemy and if it doesn't it still wastes a LOT of their action points. Or, you can just guard. It costs an action point, but if your guard is higher than their attack you can intercept their weapon before it reaches you. (Just don't do it without a weapon, that's an easy way to lose a hand.) And once again, you can ask your mate for help, since they can guard attacks for you, and even if their fail their attempt will make yours easier.

These are very basic examples, of course, but ones that are very important since combat is often a big part of the game and a part of the game that's about as forgiving as a stand-up gig at the Nuremberg Trials and good luck completing a campaign if you're bad at the combat. If those aren't good enough examples, though, you'll have to clarify because I don't know what you're looking for.