This is somewhat hard to answer with a single "good" or "bad", since some units are MUCH stronger (or weaker) in team-games than compared to 1v1s. I'll try to split it as
(1v1&2v2) / (3v3&4v4), since that'll probably give a more accurate depiction.
Which Allied heavy vehicle is the most effective and difficult to counter as Axis?
Pershing: Great / Average
Great in 1v1/2v2, especially if your opponent isn't fielding a ton of AT. Average in 3v3/4v4, since its low armor/HP won't let it sit in combat for very long - but it does do a lot of damage against infantry, so that's a plus.
IS-2: Great / Good
Same as the Pershing, except with more armor/HP, but less AI power.
KV-2: Good / Good
Very situational. It can either be amazing if your opponent is blobing infantry, or pretty useless if they have any decent AT or are micro'ing their infantry well.
ISU-152: Good / Great
Decent in smaller games, but incredible in bigger ones. It has the ability to snipe/1-shot smaller axis squads from a good distance, and also has strong AT power. In smaller games it's only held back by its cost, where it might be better to just get SU-85s for AT and some T34s for AI.
Churchill Crocodile: Great / Great
Does a ton of AI damage at good range, has incredibly high
front and rear armor, and a very high HP pool. Even if your opponent has a ton of AT, this thing is still really strong.
Churchill AVRE: Good / Good
Very situational, but it CAN be good. Unlike the ST, it actually hits where you want, so it can be very effective when used correctly. Downside is that it's still pretty slow, and doesn't have a ton of range. It's fairly easy to dodge as well.
What about for Axis factions, which heavy is the most effective available to them now?
Tiger: Great / Good
It's like a Pershing but better. It's got 240 more HP and 30 more rear armor, in exchange for SLIGHTLY worse AT/AI damage, but a faster reload speed. Only downside is in team games it becomes pretty much irrelevant against M36 spam.
Tiger Ace: Great / Good
It's a Tiger+. Still the same strengths, still the same weaknesses.
King Tiger: Great / Average
Quite a game changer in smaller games, simply due to it's high HP/Armor, and great AT/AI power. It can be a bad pick against M36s, but its great against everything else. In bigger team games, its low speed is a real problem, so it's rarely seen in "higher rank" games because of that (easy to beat with M36 spam).
Jagtiger: Good / Great
Very expensive and high pop, only good against tanks (unless you can use the barrage ability well), also exceedingly slow. In big team games it can be amazing, since it'll likely be well defended from flanking and can simply sit at max range dishing out damage. In 1v1/2v2, it's too expensive to be viable outside of rare situations; but in those rare situations it can be exceedingly powerful.
Strum Tiger: Bad / Bad
Like the AVRE but worse in every possible way: the rockets often hit the ground in front of your target, doing no damage, it slows down when reloading, it has no turret, AND the firing animation is longer/more obvious. Simply not worth the price in any way, and so ineffective that I'd consider it "bugged".
Elefant: Good / Great
Like the JT, but with the addition of self-spotting thanks to spotting scopes, but at the loss of some frontal armor/HP, as well as range.
Then there are sort of non-doc medium-heavies where you can build more than one not sure where they would stand:
Standard Churchill: Great / Good
It doesn't deal a ton of damage, but enough that its still a threat, while having absurd HP/Armor for a non-doc.
Comet: Average / Bad
Almost no one uses this thing for a reason. In big team games its basically invalid due to high amounts of AT. In 1v1 or 2v2 it can be strong, but there are better things to spend your resources on.
Panther: Great / Good
A fantastic AT-only vehicle; very effective in every type of game,
UNLESS your opponent is spamming M36s, in which case STuGs are a far better / more cost effective choice.
Doomlord52
Relic Entertainment
cblanco ★ 
