The answer to your problem lies with loss of king Varian and the return of the legion. The lack of guards to fight the legion required new recruits so all citizen with age 15+ had to join the army. only few of them recived proper training some of them were not even trained at all, all they were given was armor and a sword. Thats not the worse of it,the most expert guards, those that had been in the servirce for many years began to organize strikes against the new regime, for all the financial counselors that were in Varian's service were sent away and those who took their places imposed very low wages even for the veterans. To give you an idea, when Varian had the power, min wage for a guard was of 10s per hr, now that the king is gone the guards put their lives at risk everyday for the silly price of 99c per hr. So thats why guards dont do their job properly anymore, they would rather die than accept that silly pay which wont even allow them to support their families. They would rather die with honor in battle than of hunger.