TL;DR
Apply a random coordinates to the targeting of worm and spitter.What ?
Before, the targeting of worm and spitters shoots where you were, now they shoot where you will be.Both are very easy to predict and avoid by doing a zig zag or a timed movement (stop shoot, walk, stop shoot walk...)
Sure the combat isn't the main focus of the game and make a super hard AI that predict where you will be isn't the goal too.
The suggestion is to add two random deciders that will make it more interesting without too much work.
The first random decision would be to shoot where the player is or where will be, something like 50% each (50% chance between the old targeting system and the new targeting system). The second random would be how much precise the shoot will hit, adding a error in the targeting will make harder for just walk in zig zag or timing manners.