Every friend I have talked into buying this game has left before finishing a full game, not to start a new one, but because most battles end up being sieges, and the gates regularly opening and closing is a very irritating issue. The friend who got me involved never plays past a tier three city, as he only likes the low tier battles with all small units and only plays that far because it is War Hammer.
After this last update, I decided to test the gates again. With the HEs my Silver Helms were beating on a gate and some spearmen came to face them. The gate opened and for the first time my cavalry could fight back, though only slightly. After a moment the spearmen backed up (or were driven back) and my Silver Helms kept trickling through, very slowly.
This experience gave me hope, so I attempted a run with the VCs. My Crypt Horrors began beating on the gate, and spearmen came to greet them (opening the gate) the few that trickled through were able to fight back, but the gates closed in the middle of them again. They could no longer hit the gate because the half on the inside were fighting spearmen. Nothing behind them could attack the gate because the Horrors were in the way. On the other side of the wall, where the gate remained closed, the second unit of horrors broke through. The half of the first set locked out started running for the open gate, I guess, in an attempt to rejoin their unit.
In either case, it was nice that more of the unit was allowed to pass, even if it was tragically slow. I understand that designing a game that caters to many is very difficult. In Discussion with friends who used to play various Total War titles told me this issue is the part that made them decide not to get the next game, and that gates have been a major issue from the beginning. As I cannot get any real feedback on why you have chosen to do with the gates what you have. I really would like to help. I can see that if the gates don't open for the defender than factions like the VCs can only sit and wait, but with the gate issues the way they are, factions like the lizard men, who depend on non-flying monsters are handicapped. Trickling through allows units to be isolated. Though units continue to hit the gates while open (so they don't lose target) there seems to be no damage to the gate. And yes, you can position a unit such that it will open the gates, so they can't be destroyed, but not close enough to attack the attacker, rendering all large ground units obsolete in a siege.
I will suggest one for the last time. (and based on your reaction will determine if I even bother buying anything else.) If the gate is opened by a defender, then as long as there are any units are within the gate area and for a few seconds after (giving time for another unit to get in range and keep the gate open) the gate should remain open, allowing passage of both units and range attacks, as if the gate has been destroyed. This is more historically accurate and will help make battering rams somewhat useful again. It will allow monsters like Vargulfs and Mammoths to attack the gate, and not be isolated. This will leave a choice to take the risk to sally forth (Which was historically risky) or wait for the gate to break while archers attack other units and use the entrance as a choke point.