Since it seems all soldiers can be edited easily, I have a suggestion. This is for all soldiers, regardless whether they are guards or not.
All soldiers should more or less be the same. There might be some individual differences, especially for officers and elite soldiers, but on average they should be similar. With "officers" here I mean guard captains and fort commanders and the like, not the kind of officers the player can hire.
In the stock game, where characters get 5 HP per level, soldiers have 80 HP. This would mean that they should be on level 9. In the build characters get 10 HP per level so level 5 is enough to have 80 HP. Is 80 HP enough for soldiers? Perhaps level 10 and thus 130 HP would be appropriate. They are trained soldiers and several of them have probably been in real combat situations so a higher level, but not too high, should be appropriate.
Their Melee skill should be between 3 and 7, with 5 on average. 0 means you don't know anything about the skill at all, 10 means that you know everything there is to know about the skill, so 5 means that your are neither good or bad in the skill. Some soldiers might not be very good at fighting and should thus have 3, some soldiers are good at fighting and should thus have 7, but on average soldiers should have around 5. Only elite soldiers and perhaps some officers should be able to have a Melee skill above 7.
Their Accuracy skill is irrelevant, as Accuracy is not used for weapons like pistols and muskets. Accuracy is only used for cannons in ship combat.
Since there are eight abilities usable in melee combat, level 10 seems good enough. The soldiers are military trained, and regardless of their skill, they should have proper knowledge of how to fight, so Professional Fencer is appropriate. Professional Fencer requires Advanced Defense (which itself requires Basic Defense) and Improved Critical Hit, so following the rules of the game's mechanics, soldiers should have those as well. Since they use muskets they should have proper training in using them as well, so Professional Gunman (and thus Gunman) is also appropriate.
I don't know about Rush - perhaps some soldiers could have it, others not.
Not all soldiers are "though guys", so most soldiers should not have Toughness. It should perhaps only be for elite soldiers.
They could have two more abilities, but since they don't need any other ability than these, the rules can be bent a little so they only have up to these eight abilities.
This should make soldiers challenging without being too hard when the player needs to fight them. In general, I don't think soldiers should be fought without any particular reason. They also tend to fight in groups. I have it like this in my game and I think it works fine.
This is of course just a suggestion, but I thought I should mention it. What do you think?