I understand why you would think that more moves would be better but trust me, the arena is already complicated enough as it is haha. More moves added wouldn't help make it any easier for newer players to try it out.
There used to be a guide by Trackxyj (2nd in Arena wins, was first for a VERY long time) but for some reason when the cows started the new forum, his thread got lost in the process. I learned a lot from it even as a somewhat intermediate player. If I ever find the link to the google docs page, I'll be sure to post it in my bio.
I actually feel that the opposite would be true volcom. By adding more arena moves it would make for a larger arrangement of combinations being used (assuming of coarse that the new moves were actually useful, unlike the poison and fire....). A larger arrangement of moves would mean that your moves can work specifically with a certain gear type rather than having a combat move set that can generically be used for several different gear sets. This would, in a sense, make it more likely for a novice to win an arena due to the increased variance of moves and gear customization, adding another level to the arena.
Nobody can blame "Epics" and "paying players" for arena wins, since the majority of epics are worse than the normal gear, and since legendary and crystalline items are at an all time low cost.. New moves could change the arena dynamics dramatically, unless of coarse you want to "dummy it down" by somehow making a player win by the roll of the dice. I feel that the customization of combat moves is what makes the arena stand apart from other "luck" based games... A good analogy would be slots vs. poker, whereas slots is 100% luck and poker is a combination of luck AND skill. This diversity is what keeps many of us interested in playing the arena and if it was any less diverse, I would not be playing the arena at all.
Currently, if you are using an attack/armor gear set then you are hoping your opponent is using a defensive gear set and you are also "hoping" that your opponent is not using an armor/damage set....etc.etc.etc.
What we need is a diversification of the combat moves so that it isn't so cut and dry, thereby reducing that "hope" (which is really just luck) of not being matched up with a certain player in a certain arena, and having it be more about having a good combination of combat moves, using moves that will enhance your specific gear type.
In reality, anybody could win any arena with a little luck (I've seen it happen when low level players enter an arena a couple hundred levels higher, and still win based on the above mentioned "hope"), or the classic deflect move that always seems to activate at just the right time, except when I am using it .
I hope this makes sense.