Lifesteal is limited to 10 HP per second. Your healing will have to come predominantly from consumables like gardens.
Pocket Factory + Trees + Engineering. Your DPS mostly gets capped at 6x tier 4 weapons and turrets & mines are a way to fake having more weapons than you can carry.
Explosion Damage and Explosion size.
Most weapons aren't viable in late endless waves. Look out for these in particular: wrench, screwdriver, nuclear launcher, shredder, rocket launcher, obliterator, Gatling laser, plasma sledgehammer.
Stack ricochet and piercing
And should go without saying but Max out dodge and armor as high as you can get it
Also be on the lookout for a belt that does extra damage to elites on crit
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It says right here in Matthew 16:4 "Jesus doth not need a giant Mecha." https://i.imgur.com/dQgC4kv.jpg