Inhib and nexus turrets do really pathetic damage

Its more DOT than before. It basically makes it hard for the enemy team to force a fight under it. It also applies a slow. Ignores 82.5% of the target's armor Reduces target's damage dealt by 15% Slows target's movement speed by 10% With every hit, the beam gains 6 heat until 120 heat is reached. When the beam switches targets, heat is reset. Gains +1.05% damage per point of heat, up to a maximum of +125% extra damage 5 health regeneration per 5 seconds.

Towers shouldn't do any damage at all.

I agree. I got dived by GP under BOTH nexus towers who had no armor items at all, and all he did was kill me and then eat an orange, and he was back to full health.