I'm not sure I understand the concept of this thread. What's the difference between 'going deep' and build around? What does going deep even mean? Sorry if I'm being thick.
No, its ok. The semantics are certainly up for debate.
Build Arounds
I tend to think of build arounds as cards that you literally have to warp your draft around, so they have to be taken fairly early.
They often tend to be cards with very unique effects, and you may end up breaking singleton on them in order to get critical density.
Decks function very differently, depending on if this card is drawn over the course of the game.
Going Deep/Archetype Deepners
I tend to think of these are cards that fit very well into existing archetypes, but start to deviate them in a new, or interesting direction, adding another layer to an archetype. Admittedly, I probably need a better term to describe this.
I could have a perfectly valid UB or UG tempo deck that I've been drafting, see
undead alchemist in the middle of pack 2, and it suddenly adds a unique dimension. It fits well within an existing basic structure of bounce, counters, and creatures, but adds a new enough dimension where it begins to impact subsequent picks or deck construction.
I could be drafting a perfectly valid reanimation deck, see
living death later in the packs, and it also can start to subtly shift the way I draft and build my deck. Of course, you could pick them very early, but the effects are not overly unique, and they fit well within existing draft archetypes, rather than requiring the entire draft be warped around them.
These decks are going to function largely along the same strategic axis regardless of if the card in question is drawn.
Deck Completion Effects
This is kind of an inverse build around, and I could again, benefit from a better term. These are cards that are probably going to naturally wheel into the deck that wants them, and when they do, they perfect the strategy. They are specialized cards that you don't have to pick up early and warp your draft around, but which are the perfect cards to round out an existing archetype, and which seem to complete its identity.
In the penny cube, their are lots of great flash creatures and instants in UB, leading you naturally towards a certain deck that mystical teachings is the perfect card for.
This is different from a build around, because teachings fits naturally into an existing deck, rather than requiring the draft be warped around itself from the near start. This is different from an archetype deepner, because it doesn't take the deck into a new strategic dimension: it just completes the existing strategy, and is the penultimate card for that deck.