It's more your thinking that's inflexible Aaron than the system.
Really?
I die in one hit now, the damage being boosted is not going to change anything towards me whatsoever, actually it will improve my chances as if people boost damage, I'm just going to have higher dodge.
But as you're intent blaming this stance on some perceived benefit I would gain, I'll just explain this to you as basically as I can.
More damage=More heal costs for enemy.
More heal costs=Less people attack you
People attacking less=Less afk deaths in WL (prioritizing easier targets)
Less afk deaths in WL=more credits saved from less heals
More credits+Less deaths=more wins via attacking as one has the credits.
So I repeat. ANY damage boosting is massively unbalanced.
Due to combat edge AND basic player behaviour to take the path of least resistance.
Now that's out of the way...
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I do enjoy the idea of only one colour gem per item, but even that is flawed.
9 crystal types, and on the standard dual scythes build, only 6 are of any actual use (as nobody will be boosting speed or an attacking skill they're not using)
4 slots, 6 potentials.
If armour is only boostable on armour and the attacking skill on a weapon, we're left with 5 realistic choices into 4 slots...
Very inflexible, not what this was designed for.
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So what now? Hard bonuses still very easy to work with - they'd behave similar to combat abilities.
My ideas so far:
All crystals>Hard bonus
Fire>Health bonus
Fire>Small bonus to all other stats
limit of 2 crystals of same colour per equip
2 limit+optional 3rd with penalty of unusable 4th.
If all give a hard bonus, and fire is either health/all others, fires get to keep their prestige as high value - they're still very useful.
The 2 crystals limit means that effectively 2 stats will need to be boosted at minimum, which at least opens up a paper/scissors/rock style system.
It'd be a lot easier to figure this out if you guys could help contribute your own ideas too, rather than just effectively agree/disagree. Like how suggestions forum works...