I suggest to use of Deth lazor only if you are preparing an ambush, and the enemy heroes cant see you.
Just build turrets in bushes. Close to each other but too close. The turrets making serious damage to heroes, IF there are no lanecreeps or other NPC targets.
Use turrets to drain ammo from turrets, and for taking its aggro so you can destroy them while there are no threat.
After lvl 7:
If enemy hero is coming just selfcast (alt + spell) Xplodium Charge and run around. Let the turrets work.
However selfcast is really useful with Gazlow.
Robo-Goblin with some support can destroy keeps and forts really quickly, what means a lots of xp for the party.