This type of system leads to some lot of oddities because of checks not occurring following the approval from the action, including collision detection. One from the most glaring issues is we now have many Tera Items when hits don’t actually talk with your opponent. Sometimes, you can be standing next to the opponent, swinging your weapon, without hits connecting. Other times you could be standing too much away, just from the reach on the distance check but too far on your weapon for connecting. Personally, I find this damages immersion greatly. It may be odd to look at your character swing his weapon at thin air and somehow kill monsters.
The other issue with this sort of combat is it isn’t hands-on enough. Other than minor dodging back and forth inside the few MMOs which may have enemies with regions of attack shown within the ground, like The Secret World, your positioning is reasonably absolute and you also spend more time pressing buttons, watching a cast timer, and viewing your character conduct an action as an alternative to Tera Gold directly managing your avatar. Many players call MOBAs “action RTS games,” assuring a clear disconnect using their company characters due for the RTS influence, however character's movement and combat systems are very little different than point and then click MMORPGs. In fact, some MOBAs have an overabundance of sophisticated combat systems than MMORPG's, allowing someone to aim your attacks and understand the area of attack around the ground prior to you.