u/Low_Grocery5893

Kaya:+16 Intelligence+10% Spell Damage Amp+20% Mana Regen Amp

Veil+10 Intelligence+175 Health+18% Spell Lifesteal (Hero)+3.6% Spell Lifesteal (Creep) Active: Weakens nearby enemies by applying a debuff that amplifies any spell damage they take.

I'm not really sure about this, but isn't Veil of Discord better than Kaya for Earth Spirit mid? If not, is it at least viable as a situational item?

It makes you a bit more durable and provides additional spell damage for you and your allies in exchange for mana regen. To solve the mana issues, you could just backpack the Veil and use Bottle, or in pro games, backpack the Veil and use Arcane Boots from your allies.
Is it also possible to go for veil > bkb> shivas/octarinecore/ continue bloodstone instead of kaya> bkb> sange kaya 

I'm open to debate because I don't really play the hero.