Personally Ive grown a little tired of hearing all the talk about the armies, and so little of the people using them.
After a few battles into 8ed I predicted that the horde formation was something that would soon be a rare sight to see when people started to realize the drawbacks they had, and how easily they can be dealt with.
But lately I have been thinking that maybe there is something I have overlooked.-- First and foremost possibly that most people that use aforementioned horde formations dont see them failing all to often, because most people they meet use them also. And neither player actually exploit how brutally hordes CAN be dealt with. And none of the players have actually the tools to do so either, because they are tied up in the aforementioned horde units. (im simplifying a tad bit to try and make my thinking easier to "read")
I learn a lot of how to improve my skills in warhammer by watching sean plott, and his day 9 show, were he talks about all things related to starcraft 2. And something I have come to realize is that maybe the nature of warhammer itself is part of the reason - the slow rate games actually can be played.... and that it takes years and years to actually accumulate the necessary clear view of how the came actually is hinged together.
Whereas you can easily play 10-20 games of starcraft/warcraft in a day.
Something he talks about in some recent casts are about "its not all about whats a good counter to a certain unit, or unit composition in terms of units". You can counter anything with just enough of the stuff you choose as long as you get enough of it and pressure at the right time and place.
I have been playing combined arms msu , "Melee & Agility". type lists in all 8ed. And I fear nothing. I used to fear a whole lot of things. But 8ed core rules have solved all my issues, and all that remains are eternal bliss and joy until people start to over-complicate stuff and go nerf heavy in the comp department.
Your opponents need to adapt is my guess. And that might just mean that they need to adapt in-game with what they have. Or they actually need to change their play-style.
Would not say Empire is OP. They are good in 8ed, but so are most armies I think.
It would not surprise me if you find 8ed refreshingly easy and straight forward in terms of figuring out what does what. While your opponents does not.
I know instinctively that I would not fear the things you have mentioned as OP- because they are not by far as OP as things used to be in 7ed.
Your strongest point of OP- is the good synergy with magic and shooting. Your opponent MUST figure out what is the important stuff to dispell
They could take away your shooting- meaning they will need to bring the units to do so to the table.
They can realize your mage are a problem, and make it a high priority goal to shut her down.
The synergy between mortars and magic mostly make it possible to "kill" a unit no matter the size , so my suggestion would for them to bring less in each, and more units.
If they field mostly large units of infantry, and fail to stop the synnergy between your shooitng and magic, and dont even have the tools to do so, then sure you are most likely going to feel that your empire army is very much suited to remove enormous amounts of infantry from the table.
So to recap:
Lore of Shadow = Gamebreaking. - I would say its merly a good deck. And that people should especially be vary of the T spell.
Extra dispell dice from our Warrior Priests = Gamebreaking. nah.. just means you can stop more spells.- it breaks nothing, the game stands =)
No guess range for warmachines couppled with engineers = Gamebreaking. -- nah, in 8ed warmachines kill the stuff they are made to kill, more or less every time- its the way it works. So personally I don`t see the need for restricting double rares in the monsters category. I actually feel it hurts the game to restrict it.) Warmachings counters infantry, and monsters- support units counters warmachines, "oh" so easily in 8ed. But you need to bring them to feel it.
Hatred for cheap decent infantry = Gamebreaking. - again, its good, but not gamebreaking stuff.
Rod of Power -- Gamebreaking. The ammount you can control either magic phase with this item is absurd. ESPECIALLY when you factor in extra dispell dice for the warrior priests. -- Your opponent need to find out what 1 spell they need to stop, and stop that 1 spell. Nothing else matters.
Thats how I play in 8ed, and Rod changes nothing in regards to that.
Warrior Priests / Arch Lectors -- Gamebreaking. -- they are fluffy, and nice, and way to polite to break the game. As I type this I start to think maby you are grinning and not meaning the things you say when you say gamebreaking, or do you maby have another word for things that actually is?
Or is it the sum of all the things that you togheter find over the top, I dont know

Greg, im not with you on this one
Darn I really like 8ed. Remember the ocean of ws 10 ghouls, with "eternal" raising on 1 dice, and fear autobreak. That is the stuff you need the word gamebreaking for.
