Is it worth going to mass boss killings for money? or are splits too low to be able to get anything

No. The reward is inversely proportional to the risk, more people equals less risk.

The short answer: No.

 

The long answer: Yes, to an extent. Only go with enough people to make the boss easy enough to kill with low cost. For example, if you can 6 man corp only spending 15k a kill and getting 25 kills an hour, you will be getting 1/6th of 25 kills for a cost of 375k. That's the loot of 4.1 kills an hour for 90k a loot. This is much better than soloing and getting 4 kills an hour at a cost of 3m, but worse than trioing 15 kills an hour at the cost of 33k a kill, which is the loot of 5 kills for 100k a loot.

 

Of course those exact numbers won't apply to you personally and you should experiment to find the optimal team size for your style.

 

The same applies to nex and other bosses. Just work out how much you lose on supplies, how many loots you get, and how much you think the average loot is.

 

If you mean mass as in 100s of people. No, it's never more efficient than using a small team. But it can be more fun or relaxing, so if you were going to do nothing and don't want to do a small team boss hunt, it's better than doing nothing.

The main reasons for masses would be to just have fun or maybe if you're new to boss hunting and want to get an idea of what it's like before you head off on your own or in a smaller group. I think the biggest split we've had in our TMHT masses was 350k for an ACP. It's definitely not a good way to make money.

Like tripsis said, masses are meant either for fun or people who just begun killing that boss, so they can learn the ropes without being yelled at for screwing up. The best thing to do is mass for a day or two to learn how to do it properly, then move onto smaller teams where the good profit is at