DCC combat greatly simplifies the mess that is Attacks of Opportunity and the various maneuvers and feats to get around them in 3e+: you move out of melee, everybody next to you gets one free attack. Unfortunately, from my point of view, that works against something I regard as one of the big pluses of hit point systems: the ability to break off and run when you’ve bitten off more than you can chew or the dice are running hot against you. DCC combat is deadly enough without making retreat nigh impossible unless you were tough enough to just stand there and take it a bunch more rounds anyway.
A fix for this would be to revive one of the rules from back in the Basic D&D era, the Fighting Withdrawal. In a Fighting Withdrawal you could back up while still fighting, up to half your movement distance, and the attacker wouldn’t get a free attack (because of the phased move then melee combat in Basic, it didn’t work precisely like that, but it amounted to the same thing). Phased combat resolution and zones of control have gone the way of the dodo, and mostly good riddance, but it was handy for preventing people from zipping all over the battlefield as if everybody else was time-stopped while you’re doing your thing.
DCC keeps the essence of zones of control rules (you can’t just leave melee when you please), but makes it a little too strict. On the other hand, allowing a complete half-move while withdrawing is a shade too generous without phased movement and group initiative, since depending on how the initiative rolls went you could have practically everybody else involved in the combat take their turn while there’s still a half-move sized gap between the retreating defender and the attackers. You could allow the attacker to do an immediate follow-up half-move, but then things could get hinky if there’s a big disparity between the movement rates of the defender and attacker or if the move took the following-up attacker past a bunch of other combatants.
TL;DR here’s my proposed house rule:
You may elect to make a Fighting Withdrawal by taking a single five-foot step to your rear, if there’s room. The foe may immediately elect to follow up with a single five-foot step of its own; this takes place out of initiative order, and doesn’t count as the foe’s turn, which will happen in the normal initiative order. If this would take the foe out of melee with any of its enemies, they may also immediately take a step to keep it in melee, just as if it had done a Fighting Withdrawal. If anybody eligible to follow up a Fighting Withdrawal chooses not to follow, the withdrawer is out of melee with them.
I think this lets you do neat things like, say, backing slowly across a bridge while defending yourself, while still being pretty friendly to “theater of the mind” style play where nobody is using miniatures or marking a battle mat. I’ll be trying this out tonight.
Update: I tried it out and it worked perfectly. The caster was able to retreat out of combat without getting chopped up while his mates covered for him; it wasn’t a gimme, because the monsters got to decide whether to follow him, but I rolled and they decided the summoned bear that was in their face was a bigger threat.
Tales of the Rambling Bumblers 
This reminds me of the 5 ft step in 3e or 4e, I forget exactly now 🙂
Yeah, 3e (and maybe 4, I wouldn’t know) had a 5-foot step rule which let you take one step without attracting an attack but had no rule for following– you really were out of melee from the time you stepped until an enemy’s init rolled around and they closed the distance. I recall that leading to some very game-y situations that made it hard to conceptualize as fluid simultaneous actions, e.g. ranged attacks during that period without worrying about firing into melee.