We have very similar sieges, only reason no one takes it from the couple of guilds that hold siege is cause no one else works as a team when attacking.
And you're right, the correct combination of buffs and jewels make you unstoppable, but I think 20% chance of landing stone is sufficient enough to combat that.
We've done tests before, even with Una. He doesn't like going into arena much, but when he does, he takes like 2.5k damage from a fully built ex-ranger at most. So he can basically out heal my damage all day. But if you got the right combination of characters, it helps.
I do agree with the fact that it can be balanced, but I also agree that it can't be instant. However, I think people have been asking for such things for a pretty long time, and considering there has been nothing to indicate that anything of sorts is being worked on, people are going to get upset.
And as for what you said Vilya, the biggest, most played PC game in the world... literally only does updates based on what players ask. lol. Heck, they go as far as to take player suggestions as their newest content. They also publicly test new content/updates (even minor) on their open beta client. Game also has 0 payable advantages, and yet marks on the charts as the highest earning game in the world. They must be doing something right.