I wanted to see what Ashe, Caitlyn, and Miss Fortune were, and was pleasantly surprised to learn that, immediately, they had one synergy together--Sniper. Granted, Sniper looks like a useless synergy, but I also saw the Chrono/Celestial synergies and tried to build them up. In the process, I also accidentally activated the Valkyrie synergy and took the Blaster (read: set one gunslinger) synergy up to four.
Space Pirates sound like a better version of the original pirate synergy and I expect that to just be a game-winning comp automatically, but I haven't played around with it yet. Rebel sounds pretty useless, since it feels like a weaker version of the Shadow synergy.
Infiltrators are basically a hybrid of assassins and the shadow synergy; the shadow synergy aspect is somewhat weaker but the change from focus on crits to attack speed is one I think is reasonable enough I suppose. Still don't anticipate using it much.
Not gonna lie, the new blaster reads as being weaker than gunslingers so building blaster 4 sounds kinda troll, but I can easily see building an effective comp around it depending on circumstances. Mercenaries depending on how they work seem like the ultimate scalers.
Valkyries as a synergy sounds pretty weak, not going to lie, but we'll see how it works. Chrono sounds ridiculously broken as a synergy; it sounds like a hybrid Ranger/Lunar on steroids. And Celestial is a very very slightly nerfed Noble 6 synergy and feels ridiculously strong.
So, in actuality, will probably be building a celestial and/or chrono synergy, but hey, this is just pbe, I expect things to be different come live.
Looking at the synergies, Chrono has no secondary synergy built in, whereas Celestial does, and honestly, Celestial/Protector sounds like an even stronger version of Noble/Guardian. From those six, probably max Protector for eight, and then throw in a mystic for nine? The alternative is three mystics and keep protector at two, though you could also do mana reaver (doesn't sound op but might be), which via Shen, gives you an in to Blademaster/Chrono, for a final comp of Celestial 6 Blademaster 3 Protector 2 Mana Reaver 4 Chrono 2.
So, Celestial 6 Protector 4 Mystic 2, or Celestial 6 Protector 2 Mystic 4, or the above; Celestial 6 Blademaster 3 Protector 2 Mana Reaver 4 Chrono 2. That'd be this comp.
What makes Celestial even more busted: there's a Celestial item. This Celestial item can turn any unit into a Celestial to get healing from the celestial. And there's an item for Protector. Hoh boy Celestial/Protector is definitely the way to go here, to at least 4/2 on both of those but ideally 6 and maybe 4.
You could theoretically get Celestial 6 Protector 4 Blademaster 3 Mana Reaver 4 Chrono 2.
Or Celestial 6 Protector 4 Mystic 4.
But like I said. This is the pbe content right now, and I'm sure I'm overlooking plenty.
When the changes go live, I'll expect many of the broken combos that seem stupidly obvious to be nerfed into oblivion, and I will need to play around with what works, what doesn't, what can work in specific situations, etc.