1) The raw draw power of a card like
Professor Sycamore (and before it,
Professor Juniper and
way before both,
Professor Oak) is that they are so good, they "distort" the metagame. Decks evolve to eat through themselves
but also to win so quickly that decking out is unlikely. Decks are also structured so that the discard cost isn't as bad, either. This involves using more cards that can be used quickly (spammed),
other cards with discard effects (like Ultra Ball), and cards that are at least possible to recycle later on (plus a few cards to do the recycling).
2) A competitive game can be over in a single turn, though this is quite, quite, quite rare. Quite, quite rare is finishing in two turns. By the third turn - that is,
Player 1's second turn - it is simply quite rare for someone to have won. It is rare for someone to have won by the fourth turn, uncommon for the someone to win on the fifth turn, but by the sixth turn, wins aren't unusual at all. For example, Player 2 just had to score OHKO's against three Pokémon-EX/GX or run the other player out of Pokémon in play. The current pacing is so fast that a game which lasts nine or ten (again, that is for both players
combined) turns may be seen as a "slow" or "long" game.
3) Hala only draws four cards if you haven't used for GX-attack and
many decks prefer to use it for something significant either mid- or late game. As such, Hala draws an abysmal four cards for a third to two-thirds of the game (assuming the game even goes that long). I had high hopes for Hala when he was first revealed, but only a handful of decks really want to use their GX-attack early, and of those, even fewer are competitive.
4) Based on the period when N, Professor Juniper, and Professor Oak's New Theory (same stats and effect as Cynthia) were Standard legal, as well as for the duration of the Legacy Format on the PTCGO, running all three
heavily is the norm. Remember, just because you run three or four copies of a card does
not mean you use all copies every game; it can be just as much to improve your odds of drawing into one when you need it and/or avoiding a loss because some were Prized, some had to be discarded, etc. Until I have more experience, I'll probably go with three of each of them or maybe one of them at four. I expect Cynthia to become a staple, and possibly the main drawcard because of how stable it is relative to the other two
but they aren't going away (well, until they rotate from Standard) because Professor Sycamore is raw draw power (and many decks have stuff they want to discard), while N is that weird mix of draw and disruption that may backfire, but works often enough that it is still amazing.