DedWards

I'd replace lightning strike, or at least move that to sideboard

Intangible Virtue?

Warning. Grinning Ignus doesn't loop well with Heartless Summoning. Grinning Ignus actually requires 2 red to loop it, one to cast and one to activate its ability, and sadly, its ability only supplies 1 red mana. Now, if you had a reusable way to turn the colourless mana red, you'd be able to loop it, but the only card I can think of to do this is Gemstone Array, and it costs 2 mana to get 1 colour mana (2 for a charge counter and 1 charge counter into 1 mana of any colour).

Because you need 9 mana to entwine Tooth and Nail, I've seen people run a full set of Urza lands. This helps the deck double up as an Urzatron deck in case Tooth and Nail doesn't show. Quicksilver Amulet is another addition I've seen used.

I've actually made a deck that runs Worldspine Wurm. It can get the worm out on turn 4, during the opponent's turn (Dramatic Entrance), but it also can just ramp up into the Wurm with Llanowar Elves; Search for Tomorrow; Khalni Heart Expedition; and Explore. I stall with fogs, Traproot Kami, and Deadly Recluse. I also have a Vigor in the deck.

Just thinking, now that I have 3x Nissa, Vastwood Seer and a set of Nissa's Pilgrimage, I should look into updating the deck.

Lightning Bolt?

Hardened Scales would be a great addition

With Amulet of Vigor out, a fun fetch off Primeval Titan's ETB is Boros Garrison + Slayers' Stronghold. Because of the Amulet's effect, the Garrison enters untapped (you still have to bounce a land though) allowing you to pay for the Stronghold's effect and give the Titan +2/+0 and gains vigilance and haste, so it can attack immediately and fetch 2 more lands.

Heartless Summoning is obviously key here, and as such, you should probably try and include some search for it. My first thought was to switch out Remand for Muddle the Mixture as it can transmute for both Heartless Summoning and Myr Retriever, but then I realised it requires {U}{U} to cast and {1}{U}{U} to transmute, and that's a little heavy on blue for this deck. I still think some search is needed, though I can't think of anything at the moment.

Hardened Scales. This is pro the best enchantment for any Standard green deck running +1/+1 counters.

Increase Paradox Haze to 4x. Besides increasing the chance of drawing it, it's ability stacks.

Not sure I'd put Kiki at 4x. It's legendary, so duplicates in hand are just dead cards, but it is an important card for the combo, so maybe 3x? This opens up space for a 4th Lightning Bolt / Dissolve.

FYI, you can't use Slitherhead or Cauldron Haze. While they are black, they are also green / white, neither of which are colours of either creature you say is a potential Commander as both have only black as their colour identity. Commander rules state that you cannot use a card that is or contains a colour that isn't in the Commander's colour identity (colourless cards are allowed).

Good call. The extra life gain should upset the burn deck's plan. Other options for you to consider:
Gift of Orzhova - an aura that grants +1/+1; flying; and lifelink.
Vampiric Link / Spirit Link - one mana aura that has a life gain ability. This is worded differently to lifelink, so it stacks with itself and any other life gain effect. Also, if you put the Link on your opponent's creature, you gain the life, not your opponent.
Tainted Strike - {B} instant that gives +1/+0 and infect. Swing with a creature with 9 power, then if unblocked, play this and instantly win.
Phyresis - 2 mana aura that grants infect. Similar to Tainted Strike, except it allows you to swing for less damage over a few more turns (Tainted Strike is a 1 time effect).

Not really. I'm trying to get ready for rotation. Unless we get a 1 drop mana dork in BfZ, Elvish Mystic will be replaced by Whisperer of the Wilds.

As for other BfZ stuff, I'm torn between using Eldrazi, like Oblivion Sower; Desolation Twin; Eldrazi Devistator; and Ulamog, the Ceaseless Hunger; OR landfall themed, like Oran-Rief Hydra; Nissa's Renewal; Scythe Leopard; Undergrowth Champion; Retreat to Kazandu (I really like this one); Grove Rambler; and Omnath, Locus of Rage. The land search I have here works for both landfall triggers and ramp into BIG stuff...

If you're interested, here's the current state of my Standard deck:
http://www.mtgvault.com/dedwards/decks/nissas-forest-2/

Are you complaining about the 'overkill'? Trample + deathtouch is a frigging awesome combo of abilities. 1 damage to each creature blocking (exactly 1 in War-Pride's case), and the rest to the opponent's life. What's there to complain about?

If you can get them, Wooded Foothills would be much better than Evolving Wilds, especially when Cinder Glade becomes available.

Burn is always useful, especially mass burn or X burn (with all the mana you can have out) but I've found flying to be a big problem in my group, so besides the 3x Skysnare Spider and 3x Sandsteppe Mastodon mainbord, I have Plummet and Windstorm in my sideboard. The rest of the sideboard is still under construction, so it changes from week to week. A number of your land search cards puts lands into your hand, so Molten Vortex is a possibility.

I was lucky to get a Nissa as my dated prerelease foil, then another when I bought a box of boosters. In the same box I pulled a Chandra (who I'm trading for a 2nd Archangel of Tithes) and a Jace (who I traded for a 3rd Nissa). I'd say I was lucky there :D

Another way to 'keep' the War-Pride's tokens is Rhys, the Redeemed. Attack with War-Pride, then pay 6 mana and tap Rhys to duplicate the tokens. The original tokens still get exiled, but the copies Rhys put in remain. Just remember, Rhys's copies don't enter "tapped and attacking". Parallel Lives and Doubling Season work in the same way, except you don't have to pay 6 mana each time you want to duplicate.

To increase the number of creatures the War-Pride makes, you can use Forbidden Orchard in place of some lands. Mercy Killing is a good removal spell that gives the opponent creatures.

War-Pride is a warrior. Bramblewood Paragon gives each warrior entering the battlefield a +1/+1 counter and grants trample to any creature you control that has a +1/+1 counter on it. Rhys is also a warrior, so Bramblewood will help keep it alive long.