You guys are oversimplifying the differences between minions and towers. Let's talk about that a bit more.
* Minions can be summoned either instantly or passively in a very short amount of time. In the time a rook can set up two towers another DG can have a full complement of their summoned minions.
* Minions can have their damage, health, armor, and attack speed improved by items, towers cannot
* Minions can be healed and buffed, towers cannot
* Minions are mobile, towers are stationary
* Towers are immune to a few abilties which would affect minions, but are also vulnerable to ones which minions are not
* Towers can be teleported to, minions cannot
* Towers are generally higher damage than unenhanced minions
* Summoning a full complement of towers can cost thousands of mana, summoning minions is generally either free or extremely cheap. The one exception is QoT, and it's not a big surprise that she's the least popular DG
The main issue with towers is that they take a long time to set up but it gives the rook the unique ability to do stuff to prepare for combat between fights. No other DG really does that, and the amount of time a rook spends preparing is given a reward, which may be causing an imbalance.
I'm not saying that rook is fair atm, but you guys are glossing over the drawbacks he has and if you make him less able to hold an area and stand his ground against multiple DGs then you need to enable him to move and build momentum as quickly as other DGs who walk into any fight at 100% effectiveness. As a rook there's times when I see multiple DGs moving in and I feel like this guy getting smashed:
I know I need to move but I have no choice but to make a stand whereas other DGs would be able to escape. Also that lack of speed makes the rook is less able to chase escapees and move to support his partners. Really when you ask for a rook to be less capable of doing what he does well you're risking making his entire design concept stop working.