First of all, great game!
While playing Sentinel as my 4th class I got following feedback for you:
Melee attack-move range
This bugged me with Primalist/Beastmaster as well. You need to permanently move towards your new target before you’re able to attack again. Even if “Move to melee attack enemies that are out of range” is enabled my brave boy is just slahshing air. Please look into this!
I like the stances idea a lot! Maybe you can consider making these fixed class skills like the classic WOW warrior. You can tone them down to counteract that they no longer inhibit a skill slot. But switching between the stances to adapt to the situation has loads of more potential!