Super excited for the Vanguard . . . except for how they gain their primary resource of Entropy points.
This idea of "gaining benefits by getting damaged" has been around for a long time and it has never really worked. I remember trying it out with the good old crusader from the book of wee . . . Book of the nine swords.
So here are the problems I have always run into when using a class that has to take damage in order to use it's abilities.
1. Slow start - You have to take damage before you can do your cool stuff. Unless you are lowering your guard and running into attacks,you are not guaranteed to get damaged. Now starfinder has a large assortment of fun weapons you can use before taking damage and you can spend resolve points, but you will have to wait to use your more interesting abilities.
2. Feast or famine - You may end up getting no points because nothing is doing ENOUGH damage to you or not at all, or end up getting too many points that you lose or can't use because you are taking way too much damage. These are both issues but the first is by far the worse or the two. While the aspect trait at level 4 helps, it can only be used once per combat so it doesn't really fix the issue.
3. Self Damaging - someone always tries to cheese the system by self damaging in some way. Sure you can have the wording of the ability try to prevent this, but what is an "enemy" is up for interpretation. "Aren't we all just our own worst enemy, so me hurting myself counts right?" Point is, anything that requires a GM to constantly have to reaffirm or designate who is and isn't an enemy for game mechanics may lead to issues, both role playing wise and balance wise.
4. You should have dodged that - Damage should be avoided. If you make it in the characters best interest to lower their guard or not dodge a blow you may find they are taking a lot of unneeded damage. This will get them killed. I know there is the whole "cost vs. reward" argument, but eventually these mechanics always get characters killed. Also the death ends up not being impact full. More of a "unavoidable when you really think about it" scenario more than a "oh no how could this have happened?" scenario.
OK, so what do we do to fix this entropy point issue?
Make Entropy more Like grit points. Were dealing damage and taking damage gain us points. That way it feels really natural to go in swinging and take and give that damage the Vanguard was clearly intended to do. Possibly even make the Aspect entropy point regain work once per round instead of once per combat or have a Vanguard start the day with full points.
The Vanguard is supposed to be the front line fighter who is in the thick of it. Instead of making them the vanguards round be "I lower my defenses and don't dodge the first attack," make sure its "I charge in an bust his head open!"