Classes with two main stats in one defense are weaker defensively. This includes the supposed tank build of paladin - the Protector, who focusses on CHA and WIS. So we have a defender with two weak defenses where all his allies will probably only have one.
Star pact Warlocks need both CHA and CON to hit, so have low DEX and INT, so their AC doesn't increase with level. This makes them a striker with (at higher levels) a low AC.
Star pact Warlocks need both CHA and CON to hit, so have low DEX and INT, so their AC doesn't increase with level. This makes them a striker with (at higher levels) a low AC.