To my mind 3 'simple' changes would be enough to make siege war a real war again:
1 - towercapping only when all guards on this tower are down
2 - gates (all buildings) can´t be buffed anymore, heals to gates are reduced to 25% of actual value, damage of tornado, scrolls and players to gates are reduced to 50%
3 - rams should get high damage (breaking down after ~10s) when placed near towers.
This would be enough to make it way better than now.
The rest is fine-tuning but since Runewaker and Greedforge only know sledgehammer approaches the easiest solutions should be the first to be implemented.
1: All guards? Not going to happen, the side guards are easy enough, but the middle guard can only be taken by some OP players and even then not quickly. If the concern is Invis pot capping just make the guards able to see invis. I would like to also see something done about Warden pets in this regard.
2: Agree on buffs, but heals on gates are ridiculously under-powered. Your average healer could spend all seige trying to heal a gate back to full from a tornado hit (note I said average healer, afaik the exception is the P/Wl with his percent heal). Agree on reducing damage from tornado and scrolls; players don't damage gates to any significant extent.
3: Rams getting extra damage near towers - not sure how easy that would be to implement but I see what you are trying to do.
which brings me to a suggestion addressing both 1 and 3.
4: Have the tower guards prime directive be defending the tower. i.e. they react to the tower being attacked above anything else.