Oracle. I think I still prefer Diretide.
I don't know who this is. I quit Dota 1 around 2009 or 2010 I think when I got hooked up to Brood Wars, then immediately SC2.
But from reading, I can say Orcale is quite a decent support hero.
I don't how her ulti works exactly, but I think it's like a pseudo-illusion/invulnerability/invisibility against enemies for an ally. Basically, all attacks and healing are delayed against the allied hero. Somewhat useful for your cores, but also pretty lethal if you didn't take the supposed damage into account, and did not heal immediately. How would you know if you already taken enough damage for you to die? When it ends ofc.
I don't know how effective Purifying Flames is in conjunction with her ulti. Since it also does instant damage, and healing is overtime. The ult's damage and healing is instant afterwards, so it'll probably be good, but seeing how it heals only a few HP, it'll probably be hard. It'll be a bother to cast it after the ult, since all damage is instant, and you don't know how much damage your allied took. It'll be better to have better healing sources like Hand of God.
Other than that, Purfiying Flames is a rather weak healing method. Only as effective for allies with low current health pool. It'll be more effective as a damaging spell, so long as the enemy is a sure kill.
As for her other skills. Both Fortune's End and Fate's Edict is good. Purge is always good, and 100% Spell Resistance and 50% Damage Amplification from other types of damage can be pretty situational.
Overall. Oracle's a rather situational support. Someone picks it in pubs, and most likely they'll lose. This hero needs some getting used to before they can decently play it.
I wouldn't mind getting her, but I would still love Pit/Abysmal Underlord to be brought first. I'm pretty sure I was still playing when he came out, and before his Expulsion was changed. He really changes the game.