I'm against a Warlock using light magic.
This kind of build is generally not suitable for him (or maybe it is).
Let's start with the fact that a Warlock, properly built to level 20, can take down 8 level 7 creatures at a time.
You have to try very hard to make him take down 8 at a time, and even then, it's hard to survive long enough in a battle to get to your turn.
Secondly, the battle tactics depend directly on the Warlock's opponent.
In some cases, Chaos magic will not be needed at all; Invincible Magic will be enough.
If the opponent is, say, a Rune Priest, it will be much better not to give up Chaos magic spells.
Well...
Let's start with the fact that a Warlock, properly built...
It is practically impossible to consider all possible variations, and to adapt every event to the same scheme is more than foolish.
Except the ones we've made