Nerfs? if anything he needs a buff, his ap ratio on most of his skills is like 1/2 of every other ap champ, and akali counters anyone.
Buffs? Really? His total AP ratio of his entire skill set is 3.1. For comparison, Annie's total AP ratio is 2.15. Veigar is 2.8.
Remember, his ultimate can fire three shots, each with a .6 ap ratio, totaling a 1.8 ap ratio. Malzahar's has a 1.3 ratio, it is damage over time, and it stuns him. Malzahar's is also only single target. Xerath is AOE. The only aoe spell with a higher ap ratio is Nunu's ultimate.
Not to mention he has the longest range in the entire game while in seige mode, the only skills with longer range are ultimates like Nocturne and Pantheon, and Caitlyn's ultimate. He is also the only champion in the game with free % penetration. While in Locus of Power stacking magic resistance isn't even a viable option.
In addition to all that, his passive and high scaling and base armor stats make him one of the tankiest mages in the entire game. Only Swain and Rumble can even compare, and Swain is countered by ignite and Rumble overheats if he uses his shield too often.
The numbers don't lie, Xerath is very powerful when in skilled hands, and has the most powerful harass in the game.
Oh and Akali is countered by Lee Sin. Two of his moves give stealth reveal, which makes her only defense besides high late game spell vamp useless.