The complaints I recall about this feature is how certain abilities overlapped with one another, which was a purely cosmetic problem. I did not mind, and never had an issue with it, because it made combat flow so much more smoothly and reduced the appearance of client-server latency. This is a classic case of be careful what you wish for. Spellcasting in particular has become a lot more difficult. With how carefully you have to manage the party's HP, your MP, and the timing of skills like Spiritsong (formerly Spiritbind), every single second counts. Also, I don't know about other healers, but I'm constantly busy and juggling three different ability bars. Between casting debuffs, healing, buffing and everything else going on... that's a lot of repeated skill use. Losing the queue not only makes combat flow less smoothly, it detracts from the fun of the game and introduces difficulty from outside the scope of the game in the form of fighting with the client to do what you want it to do.