Ogres are perfectly in-line with what the monster creation guidelines in the DMG lay out as the normal process of determining CR
<snip>
And since an ogre deals enough damage in one hit to put a 1st level character out of the fight with a single hit, or outright kill a 1st level character with a critical hit, it's not at all surprising that the final CR was bumped upward from the CR 1 the math comes out to for a final result of CR 2.
The ogre should be a CR 1 creature by its stats, not CR2. A bandit captain is a good CR 2 creature.
Comparing the ogre and the captain:
AC 11 vs 15 plus a parry buff
hp 59 vs 65
Melee Attack +6 for 13 vs +5 for 6, 6, and 5
Ranged Attack +6 for 11 vs +5 for 5 and 5
On the whole, the bandit looks quite a bit tougher. Assuming +6 to hit, the AC increase reduces hit chance from 80% to 60%, which is a 4/3 multiplier to effective hp, which are already higher than the ogre. And for -1 to hit in melee it gets +3 to damage, which is nearly a 25% boost. The -1 only reduces chance to hit by one-fifth if AC is 22, which is probably not that likely at low levels. Vs AC 17, expected DPR is 6.5 from the ogre but 7.65 from the bandit.
So overall, the bandit looks something like 1.1 (base hp) * 1.33 (better AC) * 1.17 (better DPR) = perhaps 70% more dangerous than the ogre in melee. (Upping the PCs' to hit and AC will bring this back down, but the bandit captain will still be notably better. And I haven't factored in parrying.)
Perhaps the ogre
can't be CR 1 because of its potential for one-shot killing some 1st level wizards or wounded PCs. But it is noticeably weaker in melee than the CR 2 bandit captain. Curiously enough, though, the ogre is a more dangerous ranged attacker than the bandit (+1 to hit, +1 to damage) - which I find a bit counterintuitive.
Multiattack for 2 greatclub attacks would double their damage. That would up their offensive CR to 4, and 4 and 1/4 average to 2 by steps or mathematically. That would potentially make them more interesting, as you could swap out an attack for a Push to make them seem like they hit like a truck
It's been an oft discussed topic here over the years, with most people coming down somewhere between wanting more of 4e's relatively complex offerings and others prioritizing speed of play with these 'simple' foes
Doubling the ogre's attacks would then make it stronger than the bandit captain. Maybe it should be, though - it's an ogre, after all!
An alternative approach is just to allow it to Shove on a hit, with a +6 to the check (ie STR + prof). This is fairly straightforward, and also fits with its "ganging up" flavour text: if ogre 1 knocks a PC over, ogre 2 can get advantage, which takes its DPR from 6.5 to nearly 10 - which is more on par with the bandit captain. (Though not ever attack will have advantage, so still not quite there.)
No offense to the OP, but in threads like this, it's almost always ignored about what the actual flavor text is and how it impacts the game. That text is there for a reason, and monsters are much more than just a statblock. So what does the text say: "Whenever possible, ogres gang up with other monsters to bully or prey on creatures weaker than themselves. They associate freely with...." This is very important, because it means that the party probably isn't just fighting an ogre, but fighting other creatures along with it. "Whenever possible" is strong language. It's not "occasionally" or "sometimes".
How does travelling in groups affect its CR, though? It seems a tangential point.