Things I consider problematic:
1) One of the recent patches removed the increased regeneration from Combat V (or was it III, IV, V?) and put it into March (which requires Combat III). Not only did this make March very powerful (possibly more so than it should be), but it had one serious repercussion:
(Almost?) All unit classes can get Combat V, but only very few can get March (in fact, only melee, disciple and beast).
The effect? It takes much, much longer to heal than before for those unit classes that cannot get March. It's even more annoying for HEROES which cannot get March - your most powerful (and more importantly fun) units take an eternity to regenerate...
This alone is annoying, but it becomes even worse in combination with the Poisoned promotion (which all units with Poison Strength apply to their opponents after combat) - I've had units (with lots of experience) needing something like 27 turns to heal - they could not get a single promotion improving their healing rate...
I don't think allowing March for all unit classes is the right solution. To the contrary, it would make some units, like those with lots of mobility (like the Hippus mounted units) even more powerful because one would need even less turns to heal between hit & run attempts.
I'm not sure I have a better solution. I guess Combat was too strong before? What about giving Combat III, IV and V at least half their former values back (5%, 5%, 5% instead of their former values of 10%, 10%, 10%) while reducing the numbers of March in a similar fashion (5%, 5%, 5%)? Right now, March is probably too powerful (which hurts units which cannot get it), and this change would at the very least help against the problems with Poisoned...
Alternatively, one could make some other, currently underpowered promotion (like Defensive) available to all unit classes and move the entire healing bonuses from March to this promotion.
In any case, no matter what the final solution looks like, it is imperative that all unit classes have some access to increased healing - this is a factor that really slows down gameplay right now.
2) Several bugs with Wages of Sin:
First of all, several players in that scenario (and possibly others) use their world spells in the first turn - for example, the Elohim and the Ljosalfar do (Actually, I think the Elohim did something similar in Barbarian Assault). I would guess that the AI uses its world spells partly depending on whether it's on war with other civilizations - and this scenario and others have the "Always War" option enabled. In that case, the conditions for using these world spells really have to change.
Secondly, The Sheaim player starts with a Great Engineer right next to the Infernals. I assume that the Great Engineer was actually supposed to belong to the Infernals instead of the Sheaim and that it's ejected from Hyborem's territory in turn 0 because the two civilizations do not start with open borders.
Solution: Change the owner of the Great Engineer from Sheaim to the Infernals.
Thirdly, I've tried the scenario several times already and always quit in frustration after I was visited in turn 10 or so by a basically unkillable unit: Basium. (And if I actually managed to kill him, I wouldn't be happy, either, because this seriously hurts the Mercurians...). Hyborem starts with UnitAI_Defense or something like that while Basium had UnitAI_Attack - perhaps that's the problem? In any case, Basium mustn't be allowed to attack that soon personally - either he kills (or at least harasses) the player at a very early point in the game, or he dies that soon. Neither option is particularly satisfying.
Hopefully, this bug report was helpful in some way.