Here is some straight comparisons:
Hobgoblin 14: AC 18, HP 11. Atk: +3, Damage 5 + 7 = 12 if another hobgoblin is next to them. (Alone or separated, their damage is just 5).
Hobgoblin 24: AC 18, HP 11, Atk +3 (advantage if another hobgoblin is next to them), damage 12.
So what is different? Well, the AC and HP is consistent. The difference is that the 14 hobgoblin needs allies to deal the proper amount of damage. A hobgoblin without other hobgoblins next to them is doing half the damage of his CR. Whereas the 24 hobgoblin is consistent in his damage and only gets an advantage (literally) to hit with allies. It keeps the "dangerous in groups" element but doesn't turn a lone hobgoblin into a non threat.
For versimillitude's sake, you would prefer the hobgoblin's damage to be inconsistent and often times worse than other creatures of its CR. I mean, you can believe what you want, but then shut up about how 5e monsters hit like wet noodles and PCs don't fear death.