First off, let me say I absolutely love the kind of itemization Riot is introducing here. This is REALLY going to mix up the game for the better, and make every game different, while raising the potential skill cap overall, regardless of which champion you're playing.
However, it is pretty clear that certain champions are benefiting far more from these items than others. That is good, in many cases. For instance, the new Tiamat + upgrade and the Mercurial (dagger?) are going to make champs like Tryndamere and Yi extremely powerful. I suspect we'll see a new meta incoming with the advent of the melee carries.
Also, it appears that the items in general are pointing toward the offensive style of play. Particularly with stat costs being reworked. I suspect games will not last nearly so long, which should help champs that otherwise scale poorly. I may be wrong here, but there are a number of nerfed defensive items, and very few additions when compared to the offensive.
There are, however, a few champion archetypes that are going to be extremely lacking in this new atmosphere:
1. Melee APs-- While the melee ADs have received a number of AoE complements and bruiser type items, there have been no new AP items for this purpose.
2. Late Game Ability Focused Monsters - Olaf/Nasus/Veigar/etc.
3. AD Casters - I know we were told these were going to get love, but I'm really not seeing it. Where's the AD spell vamp items? The only item I see that specifically procs on -any- physical damage is Black Cleaver.
4. AD Carries -- Not sure how this will play out. If games are that much faster, it's going to be difficult for them to get farmed. On the other hand, AD cost on items was reduced, so they'll get their builds significantly faster. It almost seems like they're completely changing up the way team comps are going to work. It will no longer be about supporting your AD late, since other champs can now be team wreckers as well (and it might take the same amount of time for them all to get farmed.)
Champions in Danger:
#1 - Nasus: First and foremost, our loveable Q-farmer gained nothing that I can see from these changes. In fact, his desire to build tanky items is going to hurt him massively, as he already had a tough time sustaining vs harass from people who stacked offensive items vs. him. Add in the faster game pace and the fact that his Q doesn't synergize with any of the new abilities (and many of the new abilities remove his wither), and Nasus is in serious trouble. The only thing I see him taking away from this is less jungle pressure. Still, it's not like Nasus EVER pushed.
Conclusion: Nasus is going to need an overhaul to be remotely competitive.
#2 - Renekton / Pantheon / Talon / Zed / Garen -- Where's the spell vamp please? With lifesteal now being allowed to proc in AoEs via new Tiamat upgrade, how on earth can these champs compete with their AA counterparts? These champs do not benefit from crit or atk spd either (at least not relative to the AAers) and those are the majority of the new items.
#3 - Warwick -- Same problem as with the other melee on-hits/APs. The upgrade to Quicksilver doesn't help him either. The adjusted jungle is one of the few things that does.
#4 - Cho'Gath/Mundo -- % life burn from mages is going to hurt a lot. Mind you, if his vorpal spikes (or Mundo's W) proc the burn like they do Rylai's/spell vamp... then he'd gain more than he'd lose. (they both have built in movement impairment as well. Though AP on Mundo isn't particularly ideal. Still, potentially useful.)
#5 - Elise - No items for melee AP. She'd benefit mildly from Liandry's Lament (the life burn) but she has no movement impairment other than stun, and her two Q abilities are on relatively long cooldowns when compaired to other mages (considering the requirement to transform to use both.) The only item I see potentially saving her is the Banner of Command. This, however, is dependent entirely on if it affects her spiders (it should) and how much % damage it increases. That item will likely make or break her.
#6 - Veigar -- Same problem as Nasus with regard to farm. I also see the upgraded QSS becoming his bane. He doesn't really benefit from anything in particular, except maybe building an Archangel's. The fact that Deathfire Grasp no longer scales from AP will also hurt.
#7 - Nidalee -- Other APs have been given a number of tools to use vs her. Likewise, the ADs have as well. She, however, didn't get anything except the ability to run Archangels to Seraph's and stack tear even faster (for AP Nid.) There were no hybrid items that might benefit her either. I foresee an eventual rework here.
#8 - Olaf -- Don't laugh. He doesn't benefit (relatively so) from attack speed/crit. Most of his damage comes from his E and having a large amount of life to run amok with. Now, however, we have additional items to remove CC (thus making his ult less impressive) and life burn from mages. The only item I see benefiting him is the sheen/glacial shroud item.
Did I miss anyone?