Reworking Xerath making him a more heavy hitter rather than a "spammer"

Disclaimer: I don't think Xerath spams too much.

I wanted Xerath to feel more powerful on a single spellcast rather than having his Q and W on a shorter CD via CDR in order for him to feel like the heavy hit artillery mage I always envisioned him to be (in contrast with Ziggs who is more of a constant bomber) and in order to do so I came up with a Jhin-like effect on his passive (additionally to his mana regen on AA):

All of Xerath spells get an inner area in which they do more damage. Xerath doesn't get CDR from the CDR stat, instead his spells get to deal True Damage when hitting enemies in the inner area scaling with the CDR stat (numbers need to be tweaked accordingly).

I think this would give more spice to Xerath as he would need to more carefully aim but also get a major reward by doing so.