as a dedicated pc player who also uses a controller from time to time, I can say that whatever is the most comfortable for you is where you should go. However, if you want to adjust to a keyboard, what I do is divide the keyboard up. I use the number keys 1-6 with my left hand, but the 7-9 is done with the mouse, this also provides me having two ways to activate.
The other option to keep in mind is that targeting on the pc is far more intuitive and you have many more party target options. Try going to a simple area with a party that'll help you adjust and try the targeting options. You can use the F keys to immediately target on your party list, select that member on the screen directly, select that member with the mouse in the party list, mouse over that party list if you want to use macros as well as using text commands if you like that instead. The adaptability is the real benefit, but the other suggestion I would have is to plan your heals to begin precasting.