A couple things to clarify...

The lighting changes that are referenced in these screenshots were made specifically as a result of feedback about being unable to see enemies when the sunsets were at their back. There is no performance improvement as a result. These were made back in the 2015 time-frame.

The OMFG update, which as you all know was centered around client performance improvements, went live in late 2013.

Balancing looks and gameplay can be a challenging tightrope to walk.