My initial assumption was that as with the other modes, defending would be easier on Execution because it is simpler to hold ground than to it is to take it in Dirty Bomb. Without the ability to respawn I was afraid that offense might be an exercise in futility unless teams were stacked in its favor. After all, Objective and Stopwatch assume that the offense will fail at an objective repeatedly.
I was surprised to discover that the opposite was true - all things equal, offense has a significantly easier time in Execution. What I hadn’t accounted for was the effect of two bomb sites. The attacking team can very easily coordinate its assault simply by having one player announce “A”, “B”, or “follow the bomb” at the start of each round. This typically provides the offense with a edge in numbers that largely negates the advantages of defending ground. Once a plant is accomplished the defense team is forced to attack, but they are stuck assaulting a single target that is held by all remaining offense players. The short window of time to defuse means that even a battle in the defense’s favor can be too slow to win the round. It is also important to note that if you play an objective specialist on offense, you can often guarantee that you will start with the bomb and thus dictate your team’s tactics.
In attempting to counter this simple offensive strategy, I’ve come up with several strategies, but the problem is that they all require far more coordination than can realistically be achieved in pub play. Ideally the defense should spread out into favorable defensive locations around both bomb sites. When the offense is spotted the goals are to identify the target bomb site and to try for pick kills from relative safety. Out of position defenders need to quickly redeploy as soon as the offense is spotted. Preventing the plant is NOT the primary objective here. Rather, the defense needs to provide themselves with an edge in numbers before any potential plant.
Unfortunately, it is incredibly difficult to communicate with your team mid-battle. Spreading out on defense essentially just allows the offense to get some easy kills en route to the plant site. It also risks that your team responds to a plant piecemeal, allowing the offense to deal with only one or two players at a time. I’ve also tried directing the defense to only one bomb site and it can be wildly successful at times. The two problems are that it allows an uncontested plant half the time and that the offense has a much better chance of switching bomb sites successfully than the defense.
If anyone has found a strategy that works well on defense when playing on a team of randoms, please let me know. This would go a long way towards making my daily Execution match much less of a chore.

