My theorycrafted opinion is they needed a moderate number more Engagement-breaking abilities like the Rogue's Escape, Barbarian's Wild Sprint, and Monk's... whatever. This would allow for in-combat repositioning and in turn necessitate responsive repositioning. It may also give the player more to think about for initial formation.
Basically these Engagement-breaking abilities are a real-time emulation of the turn-based 5-foot-step, which is necessary when there are consequential AoOs. On that note every class should have at least one, though not necessarily in equal amounts or power.
For example this may necessitate a strategy like having mid-liners (like Rangers or something) to "catch" enemies that get past the front-line, and also make nuanced positioning important to reduce gaps (think Blood Bowl). Or even funnel enemies through an opening on purpose. Or perhaps you'd choose/develop front-liners that have better movement or disengagement capability rather than purely defensive "tanks" allowing the front-liners themselves to "catch" those same enemies. Or on the other hand you can design a very maneuverable party focused on getting around Engagements to get to the back line. Even then you may make your backliners maneuverable so that they can handle themselves without help.
I don't think decreasing the effectiveness of Disengagement Attacks is the right answer because I think it can be a good mechanic if implemented properly in that they are made avoidable if the right decisions are made in combat.
The problems of engagement comes from the abrupt and incomprehensible way in which it disrupts character and ai movement. Something which can affect movement so strongly should be an active power ( or linked to one, like attacking) and be limited thereby. I'm all in favor for meaningful disengagement attacks that get the power and bonus they were meant to receive. Because of the poor engagement mechanics, disengagement attacks were succesively nerfed in the betas, to the point that Josh pointed to it in a forum response somewhere.
The hardest thing about engagement is the geometric problem of when to give it, and when to proc the attac. If you wait for the target to leave range, but the attacker follows it, then you never proc. If you proc on the slightest movement, you essentially disable in combat movement... and get the ensuing ai-nightmare when a single target moving generates a flurry of instantaneous attacks and madness. I'm half convinced that the solution is tracking the distance an engaged character has moved away from its targeting enemy and then rewarding when that distance = some modifier times the targets reach. I still think engagement should be rewarded only by a successful hit/crit (maybe graze). Currently, It seems that engagement is rewarded by just having an enemy in range for a certain amount of time. This is way too passive, opinion, though you can shift engagement by targeting another enemy in range. It's all really confusing and haphazard. They should just stick with the targeting mechanic.
IMO as someone who has done various forms of combat-ish sports (wrestling, karate, brazilian-jiujitsu) the real problem with the engagement system is that it overlooks how movement in a fight actually works. It tries to do something good which is to model that simply ignoring an opponent is a deadly thing to do which is why you almost never want to show someone your back.
But it absolutely fails to model actual movement. In a one-on-one fight people don't stand still and trade blows. They dodge and weave and circle (unless they are in formation). If I start to circle then my opponent will also move, if he does not he will almost certainly give me an opening. Similarly if I back up a step they will often move.
Controlling the angle and distance of a one-on-one fight is controlling that fight. Movement provokes movement and only idiots or incompetents stand still. Footwork is a fundamental thing in fighting, easily one of the top 3 most important things.
The engagement system models incompetent combatants, it essentially assume you turned your back and ran which is a flat out stupid thing to do. In the engagment system I literally can't back up a step, which is stupid. If I am engaged in a sword fight someone they literally cannot stop me from backing up. I have to be careful and I can't do it by sprinting but I can back up and they will either follow me or disengage. At best an engagement may stop you from moving forward, but even that is iffy as you could circle. Certainly being engaged means you must move slower than a run or maybe even a walk.
Not only can an engagement system not realisticly prevent sideways or backward movement but that sort of movement should actually drag the opponent with them (if he wishes to continue to attack). So while the guy initiating a backward movemnt might lose an attack sequence, he should not be penalized for "disengaging" (and you could even have some sort of ability to say move back and then do a lunging attack if the opponent follows you). Similarly the opponent could follow and not lose an attack sequence or opt not to follow and break the engagement.
So while I laud it as an attempt at something I think should exist instead of some dumb "aggro" mind control thing the model itself is fundamentally flawed since it make the characters behave in what would be an incompetent manner and fundamentally makes fight behave in a way even amateur feel in some manner is "wrong". Note I am not saying the system should be realistic simply that the model should follow some semblance of reality. When you look at a model and the result of following that model is that the actors behave like idiots its simply not that compelling.
Unfortunately most developer's simply don't understand the intricacies of this sort of stuff. They are not to be blamed for this. Mastering this idea in practice is something that is above Black belt level in a system like karate. This is like 5th dan level stuff. But its also considered the absolute heart of a fight as well.
Combat is a flow of things, anything that forces it into something "static" is goning to feel "wrong" or "stupid".
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