If you want a monster to have the ability to heal its allies, you give it to them. Done. Now there are 4689 monsters that can do it.
I don't particularly see the point in looking for a monster that can do X, Y, or Z. You're the one designing the encounter, you get to decide what's appropriate. Say you're making an encounter with an evil artificer and his elite guardian golem. But you think the party will do a lot of damage to the golem and it won't pose a big enough threat. As one counter measure, you could give the artificer a power to let the golem spend a surge. You use it if the need arises. If you were wrong and the party is having difficulty beating the golem, and the fight is dragging on, you could decide not to use the power.
I did something similar in a fight against some dwarves. I had given one of the dwarves the ability to second wind as a minor. It seemed the fight was coming to a natural conclusion, and I didn't see point in his using his second wind, surrender was just the easier option, so that's what I did, and the ability went unused. This is why there is a human behind the DM screen. Monsters that can heal are fine. They don't necessarily increase grind. They increase the DM's options.