Her AP ratios are on par with Leona's, almost to a tee. There's no reason to build a tank as AP. Your job is to tank, CC, and take damage, not to deal damage. Ever since Volibear people have been assuming tanks can deal all sorts of damage, and this one cannot.

If you do anything for AP it is mostly just a Abyssal Scepter and even then that is only if you need more MR after Merc Treads/FoN.

Her AP ratios are terrible... and without a defensive bonus ability like Rammus and Leona, she needs that gold put into something more useful.

Everything looks good but the ralei's and the RoA, she just had too low of ratios to bother with any ap. Better tank items can go in those slots.

I was thinking of buying Sejuani, she seems a lot like Amumu/Ashe/Leona mix xD. Nice guide