Brace yourselves, this is going to be a long post.
1) Flame weapon changes:
2) Indirect Fire Units
3) Weapon Upgrades in General
4) Loiters (aka Skillplanes)
5) Abandons/Out of control
flame weapons are a bit tough. in dow2 they were all short ranged and generally limited in usefulness to garrison counters, buildings, and certain high model light infantry squads. coh2 has less mechanics then dow2, particularly relating to infantry, and so flamers are a better upgrade in general. the idea behind them is that their power against cover is the trade off for the being short ranged. in coh2 they tend to be more used as AI weapons that also preform well against garrisons rather than garrison counters. i think this is caused by a combination of upgrades generally being straight improvements and flamers often being available on either fast, or tough platforms. when these platforms also have utility functions (riflemen for example) they're pretty strong. the point of flame weapons is valid though; to allow a player to counter models in cover (ex: IS in heavy cover that can't be flanked) without having to buy and wait on artillery.
indirect fire is tough to balance, particularly at the ranges that the WFA artillery has. the OKH/USSR mortars are less of an issue because a strong push will force them to move (and they're not very accurate). reducing the accuracy of the auto fire and/or the range will make artillery require more attention without removing its usefulness against static positions. the suppression is an interesting mechanic but is pretty broken on units with as much range, accuracy, and as high a fire rate as the pack and lieg.
weapon upgrades just don't have the variety that they did in dow2 because of the simpler mechanics. you no longer have melee, stuns, heavy infantry, or fantasy abilities like teleportation. there's still the potential for interesting upgrades though (GzB 39 providing light indirect and AT for example).
planes are tough; there isn't a complete system in place for them. as a rule of thumb, each faction only has one AA unit and those units all preform roughly the same. they generally stop loiters but not always before the damage is done and the single passes they never stop. personally, i think the game would be better off without planes but if they have to stay in they should be powerful but give AA units an opportunity to shoot them down before they do a ton of damage.
i don't really see your issue with out of control but crits in general are RNG (baring snares) and RNG with something as important as a tank is not nice, especially when the abandon crit can potentially transfer resources from one player to another.