The biggest offenders are the most overpowered powerups and weapons (including their respawn frequencies):
- Rune of Invulnerability (both the Human and Dragon variants),
- Magma dragon weapon,
- SoulTaker,
- LifeGiver,
- Dreadnaught.
Let's put that into perspective: the Dragon Armor (nowhere nearly as OP as the runes) respawns every 90s by default... arguably still too often, depending on # of players and the map in question.
Magma weapon is almost as bad - its respawn timer is only 60s.
Normally, its huge energy use limits its overall usefulness when there are many players - but with only 2 or 3 players, the winning strat becomes to grab the magma and patrol the area where the entrance to its location is (and/or grab the invulnerability rune, as well).
In open areas, a decently-aimed alt. magma shot will usually oneshot the opponent - and with only 2 players, there's plenty of time to recharge for the next shot.
SoulTaker: 40AP damage... that's enough to be instagib when used with the spin combo. And because it's AP, the type of armor worn (if any) makes no difference; that makes fighting a skilled, SoulTaker-equipped opponent extremely frustrating, with only very low chances of success due to serious risk of instant death.
Also, its 30 durability is just ludicrous for such a powerful weapon.
LifeGiver: with 25AP damage, it's not quite as powerful as SoulTaker (will never instagib a fully-healed opponent) - but that disadvantage is more than offset by its healing properties (40% of damage dealt

Again, that is not a problem in and of itself - but once more, the durability (30) seems excessive. That's enough for 3 full heals; or far more if used in combo attacks.
Dreadnaught: With 80AP, it's a 2-hit kill if used with a regular attack, and instagib when used with any combo (other than the forward thrust). Which is actually OK, since it's supposed to be a very powerful weapon.
What's not OK though, is its extreme durability - 15; easily enough to last half the duration a typical 20-kill map.
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So here are the changes which I propose to implement (in next release of the Community Patch):
- Increase respawn timer on the Magma dragon weapon to 100s,
- Increase respawn timer on the Rune of Invulnerability to 150s (dragon version) and 75s (Rynn version),
- Decrease the SoulTaker's damage output to 35AP (from 40AP), and its durability to 20 (from 30),
- Decrease the LifeGiver's durability to 20 (from 30),
- Decrease the Dreadnaught's durability to 10 (from 15).