One ship can definitely take out a heal ball on it's own. I've seen it done, I've done it. Of course the difficulty of doing so will vary depending on the team you face, but it is most definitely possible. Anti-nuke lasers also have a considerable cooldown. Disrupting, purging, or just waiting all result in the ability to nuke. And yeah, people in squads are more likely to say healballs aren't a problem because they're also more likely to be experienced, and/or older players.
I've done it too. But as you said. It is dependant on the team you face. Nukes also have a long cool down. So Nukes vs ANL is mute really. I do think OB's are the real problem over healing it's self.
Nukes vs ANL is not moot. Ships with nukes are destroyers and dreads. Destroyers are capable of launching up to 4 nukes on their own within a short period of time, and they aren't affected by ANL. Dreads, if frontlining efficiently in tandem with retaliator can be launching nuke(s) every 10-15 seconds. The ships with ANL are corvettes, artillery and destroyers. Ill be damned the day I see a corvette with ANL, so it comes down to med-heavy dessies and artillery. So again, no. Not moot.