Currently, boss tasks are rather lackluster. They kind of always have been.
There currently are 5 boss tasks: Chronozon, Kalphite queen, Chaos elemental, KBD and Wildywyrm. I have done plenty of all of them and none feel like they're worth it as a task. The tasks are too short to get any loot without being really lucky and their exp and slayer point reward is not really worth going out and killing the boss for. You get 5 kills per task max, and you can do plenty more kills in a trip with most of the boss tasks.
Extending the tasks
The damage bonus you get from being on a slayer task will very often get you the kill when grouping. This would be a very nice bonus to have for a trip or two, but the current amount of kills we need for a task is rather low. Increasing the kills needed for a task could mean that you would be guaranteed an easier time killing the boss while having a large chance to actually get some loot during your task. It would be a lot more satisfying to actually get a boss task that way, though the chance to actually get one would have to be lowered as every boss would be crowded with people having it as a task. Or, as mary suggested a while ago, you could get a boss task as an optional thing after having completed a certain amount of tasks in a row.
Adding rewards
More slayer points, simply put increase the slayer points you get from a task. Increasing the amount of points per boss task wouldn't be as impact slayer point gain as much as it used to due to cancelling tasks now sinking a lot of the points. Boss heads could also be a way of adding more rewards, having them traded in for cash or points would be nice. They would only drop from the bosses when they are your active task.
Additionally, the other bosses could be added as a slayer task.
