It depends to what extent you're being reckless. It also depends on two things: the amount of harm you're doing to your team, and by way of that, what the faction you're hired on for feels about your actions.
The opinions of the team you're on matter in cases like this more than elsewhere, and admins tend to defer to their feelings about it before kicking most people for griefing strat battles. If the faction that hired you is okay with you skirmishing by yourself, you're fine. If you're doing well, despite them not wanting you in the field, you might be okay. If they don't want you out there and you're not going positive on kills, you are on thin ice. Suicide leeching/running in to die without fighting takes on a new slant in strat battles where it also falls under griefing rules.
A chinese clan attacked me on strat a month ago, now i see they have a battle up.
I want to join on their side and just charge solo constantly and waste gear to lessen their chances of winning.
Are there rules against this? 
This, though, is an example where the faction's opinion might not even be called for. That's pretty much the definition of strat griefing, right there. Don't sign up unless you're going to actively try and contribute to your team's
success.
Yes, it is against the rules. It is the kind of thing that gets a person banned.
If you ask them beforehand and they say it's okay that might be different, but it would be rather far-fetched considering your goal is to assist in their downfall.
