The nature of Clan guns means that just about any Clan DropShip has the firepower to be a decent space combatant. Essentially, there aren't any undergunned Clan ships. Instead, the things to look at are thrust, armor, and heat dissipation. At 4/6, Clunions are above the average for spheroid ships, though not enough to be considered particularly fast. This does serve them well in the escort role, as they can keep pace with anything a 2/3 or 3/5 WarShip can do while still having a bit of thrust left over to orient on incoming threats. Like the thrust, 280/210/160 armor is good without getting into the realm of overly tough. You can survive the firepower that's gonna be flying around, and are tough enough that the amount of damage needed to kill you quickly is gonna be hard to bring to bear when you're trying to focus down a WarShip. In terms of heat, Clunions are excellent, able to fire everything without making the power grid so much as blink. This is good for an escort, because regardless of which way you're pointing out how many targets you need to engage, you can fire at whoever you want.
If the Clunion has any weakness, it's in the weapons arrangement. The bulk of the guns are in the forward arcs with the aft quarters actually being rather anemic, so while you can fire in every direction, some of those targets simply aren't going to have that much firepower pointed at them. This isn't that big a problem in the WarShip escort role, for three reasons. First, most WarShips prefer to stay at range, so in most cases the main threats are all going to come from one direction. Second, the nature of ASFs versus big ships means they don't want to swarm a ship from all directions because that spreads their firepower across too many armor facings - they need to concentrate all their shots on one direction if they're going to chew through a WarShip's hide in any sane amount of time. Even if the fighters attack from a different vector than the large craft, you're still looking at two, maybe three threat axes at most. Three, escorts usually come in groups. It's not hard to point one Union to engage one direction, and a second Union to engage another.