Archers and Tower of Light shouler options are a must in my book. They give you that added firepower and they help deter enemies from chasing you.

The trebuchet is a bit questionable. It's got a nice range, and I'm not sure about the damage, but it tends to give your position away due to its long range... However, the poisoned arrows seem like they could be pretty effective.

Archers and Tower of Light are a must as must people have said, trebuchet and poisoned arrows are situational, trebuchets are good to kill towers and if you are killing faster demigods, poisoned arrows also good to hunt demigods and to slow them while you run, so trebuchets i get them if im pushing constantly or if i spec for demigod killing and poisoned arrows if im speced for demigod killing.

Ohh, I had no idea the shoulder upgrades gained damage for the upgrades after them, does poison arrows increase it too?

Trebuchet also targets structures and slowly wittles them away without you having to get in their range.

The trebuchet is a must-have.  Poison arrows is something you can get if you want, but it's not necessary.  However, I've had several games where the turning point is a level 8 rook that gets his trebuchet.  The tower of light is an invaluable extra attack.  Curiously, I've had countless kills where an enemy with 50 or so hit points is running away, and the final blow is dealt by my arrow towers.  They're very useful for dealing that last pinch of damage to a retreating foe.

What do you mean chaining?

Chaining is when Towers that are close to each other share energy to power up one Tower, increasing the damage it causes.

This has been proven thus far by Rook veteran players to be false, using in-game dmg statistics.

The chaining is nothing more than a visual effect : it neither increases range (confirmed by same damage output regardless of amount of towers chained) nor power (again, multiple towers chaining did not increase damage at all).

This may change in the future, if Stardock decides to modify the Rook's towers.

It is indeed misleading though.  Maybe during development, tower chains were powered up, but this wasn't the case in the beta, and neither it is as of this date of the official retail launch.

Ah, my bad then. I have read in several different places that towers can increase each other's damage, and I assumed it was true since the graphic effect seemed pointless without it. Thank you for correcting me.

also worth noting, treb has a small aoe