The Good, The Bad, And Pugna (mostly done)

This looks more like a guide already =) Still needs to add some usage and a part "When to pick pugna"

BoT = Boots of Travel
imho = In my humble opinion

Nether Ward needs to be maxed before Decrepify. One or 2 levels of Decrepify is enough for most of its utility as Nether Ward does wonders against the first pushes.

I also disagree with Necronomicon as you have such a great pushing potential that with a BoT you can basically overpush a tower easily anywhere on the map. On top of that, they give true sight (awesome against a nasty rikki for instance) and keep on hitting when you cast decrepify on yourself against physical heroes. It's situational but I won many games by strategically pushing with BoT+Necro.

Eul's is core to me as pugna lacks of survival and stun
-> A Sand King blink with his ult? Storm Hammer or Magic Missile heading to you? Double tap Eul's.
-> Shadow Fiend, Pudge, Sand King, Enigma, Witch Doctor, Sniper casting ult? Send them looking at the clouds instead
-> A hero tying to TP around you? Learn to tell him "No"

You also forgot to talk about Pugna's awesome base MS. One of the best base MS in the game. With a double damage at first rune spawn, you can nearly catch up any hero.

Black King Bar is nice but I would not say it's core. I mean, you are support, and you have an awesome ult. You do not have some kind of awesome skill that require Bkb. The only skill that does massive damage (in late game) is your ult and it has no CD (in late game, you must have scepter anyway). I'd say it's situational but well it's a detail.

Not finished I guess (hope).

About the boots, BoT is way better imho.

Nether Ward priority can be discussed but there is such a lack of information that arguing would be a waste of my time.

To be continued then...