I think investigator is probably the best jack of all trade Inquisitors are strong as well, but I just think studied strike is a little overtuned.
1. Studied combat caps out at +10 to hit +10 to damage and isn't limited to a particular weapon type, studied strike is ok, combat inspiration and access to mutagens are awesome.
2. Good variety of spells from the alchemist list (not really a lot direct combat options, but lots of strong buffs, heals and defensive options).
3. Alchemist spell casting isn't subject to spell failure from armor, so with feats or by taking one or 2 levels of fighter.
4. d8 hit dice good progression on will/ref, can use inspiration on must pass saves, not super MAD so you can afford to start with a 14 con usually, access to solid defensive spells like shield, mirror image, and stoneskin.
5. 6+ int & int based spellcasting, inspiration for free on int based skills, lots of free skill points for social skills.