Illusionist's bracers will only proc for Festering Newt, which will make that card problematic for use. You'll have to pay 3 every time you summon Newt, and hope you have newts. You bump into a deck that runs exile, and your screwed.
Running three erebos seems a little... much... to me. Considering it's a legendary, so you can only have one on the field, and with the deck size it won't really take much to get it? Espescially with four tutors. The same goes with Sorin. 3 is a bit... much... espescially given the costs of both. You'll pretty much just be tossing cards into your hand that you can't play.
Might I suggest grabbing some cards like gods willing? 1 drop instants that grant protection will keep something from just exiling all your newts and erebos. Otherwise, your asking to get smacked with something to disrupt the flow of your deck.
This deck is very vulnerable to white and red decks with a lot of exiles. Just running some Pillar of Flame or Devouring Light will leave this deck defenseless.
Something to destroy artifacts will do the same thing, since once those cauldrons are gone, your done.You might want to consider getting something to account for that- Loxodon Mender or Darksteel Forge.

Thanks

As an aside- High Priest of Penance is a good card, it just doesn't work as well in this deck as some others. This deck is looking like a very strong rat token deck, and HPoP needs to get hit to kill something. You have nothing to damage it yourself, so it's just a 1/1 that might as well be unblockable unless they run multiple walls.
This deck craves something that's a little more instantly gratifying.

If you want to keep the white splash up, consider instead a pulling high priest of penance for a couple Banishing Lights. The exile capability will seriously help this deck.

Scrap the thoughtseize cards and add some kill spells. Doomblade or something. Thoughtseize is good, but it'll only go so far.
Also, consider scrapping High Priest of Penance or something of the like for some Tragic Slip cards. A deck with a good indestructible/regen pull would wreck this deck, but you cannot regenerate a creature slapped with -13/-13, since regenerate only removes damage and pulls it from combat.