I do admit they are glitchy, but I find sieging a bit too easy (Difficulty 107%). I personally am a strategist, and sieging for me is a combination of correct troops and the right strategy. If you have a strong character, then tell your infantry to follow you and when your half way up the ladder tell them to charge. About the time you get to the top, they will be right behind you. You don't have to worry about them knocking you off, and you can get up the wall easier.
With your strategy, I use my archers to fire on the towers while I lead the infantry up the wall. I clear the main battlements, then get the archers to hold position right by the ladder. I lead the infantry to the courtyard to fight the enemy, then I tell everyone to rout out any small pockets of resistance that might have survived the initial sweep. Because of the archer cover, there is minimal fire while you climb the ladder, then because they guard the ladder, they both cover your infantry as they come up and assist you in the heat of battle.
Now if you can't comprehend that, and I'm not saying you can't, but in general, the only other way to really win is to preform a barbarian type tactic and just outnumber - out power the enemy.
Good luck, and just have fun.