Not much use sending out Spears and bows (unless you're an Elf...) on attack. The whole point is to be able to use defensive troops in a siege situation.

makes no sense

Not necessarily.  I think that game mechanics should be designed to be as fun and interesting as possible, even if they are not strictly realistic.  I don't know whether the proposals outlined here would make things more fun and interesting, but I think that fun and interesting should be balanced with realism, hopefully with a tilt toward fun.

They should fix that asap, and enable blockades again.  @Quackers, I don't get your idea, doesn't sally forth already do what you want for active defenders?

Yea I guess it does, guess I'm just trying to think of more ways defending troops can be useful. (before pathfinding) :P

Why are battering rams allowed to roll up to the walls and attack at will?  Rams suffer no risk when attacking walls even if the attacking force is vastly outnumbered by defenders.  Battering walls is an offensive action and should trigger some sort of combat.  Why don't the troops outside the wall need to successfully raid the walls each time (or once a day) the rams are used?  As it stands now, you can send rams with defensive troops and they work just as well as rams with offensive troops.  Then when the walls are down you can send in cav to wipe out the defenders.

What is the point of walls if the only way to protect the walls from rams is to sacrifice their advantage and attack the besieging force?

Along the same idea, why can't attacking troops destroy farms, quarries, mines, pits and lumberjacks without catapults?  Aren't those things outside the walls?

Siege armies move slowly so you have a lot of time to prepare.

Step 1: Scout attacking town with advanced scouts, to see army composition.

Step 2: dodge any direct attack on town (most players will try to wipe out any forces in defending town before siege lands)

Step 3: When siege army hits the town it will need around 10 minutes to set up camp. In that time you should send out your defenders to most likely siege position, based on scouting information. Your defenders move faster than siege army so they will be there first (occupy for 10 minutes). Usually there aren't many good siege positions, but if there are you can always split your army. With new map arrow movement indicators you may actually see where siege camp is going to land. I haven't tested this map arrow hypothesis though.

Inexperienced attacker will just sent siege army with many defensive forces and will not hit siege position with cavalry/infantry few seconds before siege lands. Such an attacker is easy prey for defensive forces...

But primary role for good defense force is to actually siege yourself. Good defenders are most dangerous in this game, since siege is ultimate attack and you need many defenders for sieging...