Actually I'm currently having a very fun and challenging game with Byzantium
Got through all the early slavic barbs, Sassanids, plague, Arabian and Bulgarian spawn without losing any cities, but boy it was close a couple times

(maybe I even lost Sinope once for a couple turns, I'm not even sure anymore)
After this I managed to crush the Seljuks, by the time they came almost all of Anatolia and Egypt was settled and the defences built up pretty well
Having said that, early barbs will be reduced, watch out for the upcoming patch 1.11
But still not sure what's the best way to solve the barbs-plague-spawns triangle
Yeah, my game is going well until now (3 turns to bulgarian spawn), but I'm sure it was luck what saved me until now. Sassanids are a lot worse to handle then Slavs. A couple Swordsmen can crush all Axemen, Spearmen and HAs (actually I've seen none in this attempt, only a single skirmisher) from Europe, but the Sassanids can only be handled within your cities. 1,2 or even 3 axemen/spearmen coming from outside your borders cannot be compared to 2 lancers spawning inside your borders, right outside your city, and another 4 outside your borders with neutral roads to reach Sinope, Aleppo and Caesarea in 2 turns.
Lucky points:
- Lost no battles of ~70% odds. If I had lost a single battle, I would have lost a city;
- A Sassanid that could destroy Tyre easily moved back to Aleppo to be crushed;
- 8 Lancers attacked me in Aleppo (no walls) on the same turn and lost all battles (I had 2 archers with no upgrades and 2 spearmen one Combat 2 and the other Combat 1). More 3 attacked me on the next turn, 1 lost 2 won but got hurt, and on the following turn I destroyed them;
- I removed the Archer from Athenai one turn before the plague got there. This archer sacrificed himself to prevent an Axemen to get Athenai from me;
- The Plague started in Alexandria, then got Greece, then Tracia and Constantinopolis, then Smyrna, Nicaea, then Iconium, Cyrene, then Tarsus and finally Caesarea and Tyre, so even with the hard time in Greece, because of the lack of plague in Eastern Anatolia I could survive the Sassanids;
- I won a 20% odds battle against the Arabs with my first MS, then the other 2 and the Khazar had to handle the other archer, the last battle being 80% odds and luckly I got through.
The game is going well, but if luck wasn't on my side I should have lost Greece, Tracia, Sinope, Caesarea, Aleppo, Antioch, Tarsus, the Levant, Egypt and Cyrenaica. Maybe even as far as Iconium.
I have a suggestion for the plague-spawn-barbs triangle: If we could recreate something like what happened in my game. I don't know if the plague can spread not exactly random, but semi-random. If the plague avoid the Levant and Eastern Anatolia, at least for most of the time, it's easier as you'll have your hardest frontier at least secure. And besides that I think the plague should be less severe. If it's intention is to mess all your cities, at least make it swift. The way it is now is terrible: I had 10 full turns of plague (628 - 668), Hadrianopolis got it twice, and most of my cities got it for most of the time (the first city to be free was Hadrianopolis, then it got the plague again. Only 2 turns to end the plague the cities in greece and egypt got safe). Only Sinope, Antioch, Aleppo, Jerusalem (and the city I built, Gaza) didn't get it.
BTW absinthered, is there any reason for what happened with my stability in the case of Gaza? Losing 7 pts of stability in a Solid province in the beginning of the game? I know there are penalties for big empires, but I wasn't losing this much of pts with my 1.0 Byzantine that streched from Mus to Pamplona (I know I had Krak and Militarism, but this is not reason enough)