I haven't seen anyone bring it up yet, but IMO the most broken thing currently is the Wehr luftwaffe doctrine. You can drop fallschrimpioneers at the start of the match, to get better positioning. All well and good. But then those pios can build the 2cm flak emplacement immediately, which not only has insane range, but kills light vehicles (including light tanks), murders infantry, and is almost literally impossible to destroy. Dealing damage to it only decrews it, dealing no damage to the emplacement itself. If the enemy has a nearby halftrack or squad (spoiler, they always will), they can recrew the emplacement and keep it at full health.+
One of these emplacements can basically shut down an entire section of the map for long enough to rush out a fast P4 or Wirbelwind. In 1v1 its not such an issue since you can go around and go for cutoffs, but on 2v2s and up, this emplacement literally wins games for free. The only counter is to win the opening engagement hard enough that the wehr player cant build one, then keep them off key points until you have tanks so they are not a big issue.
