Riding while an amazing skill, is really limiting when it comes to Sorc pairings with other classes. If you want to use Riding to the maximum you have to be on the Summon auto attacking and using its attacks to benefit fully from the attribute. If you don’t to use your other skills from other Wizard classes you miss out on some heavy hitting spells.
My suggestion is to rework Riding into a new skill called Sentience.
Sentience
Cost X mana per second while active.
Infuse your Summon with life allowing it to use it’s special skills on its own. These skills will target the sorcerers last target or can be force attacked to focus using skills on a single target.
Attribute
Sentience: Damage Up
Increases the Summon’s Physical and Magic attack by .5% per attribute point. Gain an additional 10% at attribute level 100.
This would fix a few issues with Sorc mainly being they suck paired with other non summon based classes and having to be on the Summon riding to deal damage and use their skills.