I wouldn't call them OP, per se, but they have noticeable advantages in the early game that can quickly allow them to snowball and heavily contain the germans from establishing any sort of foothold.
I'll quote myself from another post to explain:
Does no one feel like Allies' early game is too powerful? Seems like the majority of tourney games are won by Allies because their play style is easier (build a horde of units early game, dominate map, push momentum). I.e. Face roll. USF works almost entirely this way: strong early game but weaker late game which leads to a lot of games being decided in this first 10 min.
- Granted the advantage is small - I think balance is in a very good spot - but is exacerbated in high level play where the flow of resources can stack up quickly against you.
- I didn't see much British play in OCF and for good reason: it's like playing Germans! You're early game hangs on a razor's edge and you try to fortify to make it to the big guns. Why go through that when you have a strategy that basically guarantees 60-100% of map control as Soviets/USF.
It has always felt like Germans are on the back foot. One wrong move and your defensive line crumbles and you'll never get the map back since Germans are generally awful at assaulting positions. I mostly attribute this to map design and general army design:
German infantry tend to do better at long range and in cover
But Allied infantry have an advantage is most other scenarios (medium/short range, no squads in cover, assaulting positions). Because of this, small maps with lots of corners and shot blockers (most of the 1v1 map pool) generally give the allies an edge since it's very easy to run around with Riflemen/Cons and just charge any Grenadier you see.
Germans, on the other hand, rely extremely heavily on positioning. If you're MG is not far enough back but not far enough front, Grens not in cover, no AT gun at 8 min (to counter halftracks), tight spacing - whatever - there's all sorts of things you need to execute very well to stop the Allied assault. Why do you think Mechanized Assault Doctrine or Close Air support are so popular? It's because they cover the German weakness in teching very well. While their teching price is fine, it gets very hard to try to even get tech 3 as Ostheer because Germans are usually so fuel starved from low map control.
Germans play a lot like Space Marines from DOW2 (and if anyone played that game you would know SM were one of the weakest races throughout most of that games history) - they have a very powerful army when supporting each other, great late game units, but extremely weak at independent missions (Sending units solo) and mobility. This forces Germans to send 100% of units to a certain defensible sector of the map right off the bat or else risk losing all the map since your squads will generally lose to their Allied counterparts.
It's hardly surprising the more mobile and aggressive factions do better in a game where you must fight across the map to win instead of being able to hunker down in a base. It was like this in DOW2 (Where Eldar and Tyranids were the most competitive factions, both armies extremely mobile and cost effective) and it's like this in CoH2.
However, some maps work very well for Germans because they are big, open, and defensible (especially Langreskaya). Easy to spot enemy advances, dependable cutoff, "natural" VP, wide areas for MGs to take full advantage of their range. Most maps though have a lot of shot blockers (especially around critical cuttoff points) or bottlenecking points of advance that make it really hard to push out as Germans with your long range army.
TL, DR: Allies have early game advantage that puts the game in their initiative (a fact shown in their dominance in tournament games among high skilled players).