Celebrim
Legend
There's nothing wrong with a gonzo campaign, they can be fun. I want my campaign a little more based in reality.
The problem I have with a gonzo campaign is that they have implicit or explicit meta-rules like "the rule of cool" or more likely "the rule of funny" where rulings are made based on the GM's desired outcome rather than based on any sense of fairness. This makes it almost impossible as a player to predict how a GM is going to rule because "cool" and "funny" are such subjective things - imagine the GM has a sadistic streak for example.
There are an almost infinite number of problems with the ballista strategy. First, it's not going to be easy to hit a flying target with a large siege weapon. So I'd pretty much be expecting the PC's to spend a 'True Strike' or other spell resource to get this to happen outside of luck.
But this also has to happen with the ballista trailing a stout line. Weight matters here, so range has to be more or less point blank or that ballista bolt is running out of energy. If this isn't a silk line or other high quality rope, I'm applying penalties even to a point blank shot . And getting that point bank shot probably involves luring the dragon successfully in some manner, and that involves a beast that has super-genius level intelligence and the eye-sight of an eagle. So unless there are some really good distractions going on, that dragon knows exactly what you are up to and will bemusedly counter your plan.
And hopefully your amount of spare line exceeds the range of your shot, otherwise you just found a really interesting way to violently trip yourself.
Then the ballista bolt has to actually get lodged in the dragon, which for me would be a damaging critical hit. And there aren't a lot of ways to ensure critical hits (for very good reason). Most plans would just fail here. The bolt did hit point damage but not enough to become lodged.
But even if you do lodge the bolt in the dragon, nothing suggests that that line suddenly going taunt isn't simply going to rip the bolt free. That's a tremendous amount of third derivative of velocity with respect to time going on here. There is also the problem that if the bolt doesn't rip itself free, the second weakest point in this system is the PC. Hopefully they didn't tie the knots wrong, and hopefully they tied it around a durable part of their body. If it is around their leg or something, the next fortitude save is going to be for their hip socket.
But even if by a miracle this all works, the dragon is a four legged beast with manipulative digits and a serpentine neck and a very high intelligence. The PC is just separating himself from the party at a high rate of speed in an environment he has no real movement rate in. The PC has definitely not thought this through, as the dragon can certainly bring more resources to bear in this situation than he can. This is creative suicide, not a heroic action.