In this day of moving shot and spammed special moves, would it unbalance the game if mage's did not have to stop to cast? What i see is people using a wonder aid, and bailing off screen before i can get an e-bolt up. plus they have time to chug also.
Your thought's...
It's not really specific to UO. In pretty much every MMO there's usually a movement restriction on casting, or at least casting any "serious" spell. Healing almost always forces you to be sitting duck and take damage or get killed trying to pull the spell off. And most of the "worthwhile" (cast time and mana rate : damage ratio) spells are on relatively long timers and require you to stand still.
Unfortunately, as online RPG's (I use the term loosely) have morphed more towards pandering the action game and casual gamer crowds, they've become faster-paced with more frenetic action, fast-speed running or movement abilities. There are games for instance (I'm staring down WOW with one eye) where even from day one, the cast timer on many offensive spells was longer than the time it took for someone with default, vanilla movement speed to run out of range of the spell. I don't really understand the logic of that given that casters tend to have the poorest defenses, lowest health, are easiest to kill in close range, and to top all THAT off, tend to have their spells interrupted when they take damage. These are more or less universal statements about casters in MMO's in general... relevant to, but not exclusive to, UO.
What's emerged are cheesy tactics which serve to hem in... if not outright marginalize casters in online games. Speeding into melee range, hitting, and speeding back out of spell range before a caster can react would be one. Or getting into, and staying in, very close range with a high-speed attacker (say fencing in UO, or a rogue in WOW) so that spell interruptions remain so consistent and frequent that the caster is unable to react or defend himself in any meaningful way. Add in WOW's case the super cheese tactic of how you can hit with melee weapons from a good 270 degrees around the front of your character... but a caster pretty much has to be facing (within a 90 degree pie or so) directly at his target in close range in order to fire a spell or else he gets a "You must be in front of your target" message when you try to cast. This gets exploited because in the high-speed fast-paced nature of WOW combat melee simply spin around you in a tight circle, stabbing you all the while, continuously breaking any spell you try to cast with a "the target is not in front of you" message. (Your character does not auto-spin to keep the target in front of him while casting.)
I think that in "old school" fantasy/RPG, the tradeoff for the many downsides of casters was that they had tremendous power packed into their spells... and could do more in a shorter time than a melee could, though they might be exhausted afterwards until they re-memorized spells or recovered their mana. Melee traditionally filled the role of being more "consistent" damage takers and damage doers--- not capable of fantastic immediate devastating performance, but solid and would hang in there reliably throughout a longer period, not relying on burst damage and then having to back off and recover. This has changed.
In online RPG's, the standard has virtually become the opposite. Mages and casters tend to be, with the help of mana regen and similar gear mods (which they more or less need) do a fairly consistent level of DPS from the background. Melee tend to be up front able to take damage best, and able to deal it out best in short spurts. (Unlimited high close-range DPS if there is adequate levels of healing and support... a role in which the caster often finds himself consigned in many MMO's.)
I think a lot of this is gear changes which have become normal. The game starts with set damages on spells.... not on what a melee can do given the right damage weapon. When games keep adding gear, the level of damage melee can take, and dole out, tends to significantly ramp up (better armor available, better weapons available) while gear changes to the damage casters do tend to be almost afterthoughts or slap-on's, with the base damage for spells usually not changing even through major patches or expansions. Casters I'm sure can still do sick damage in a couple of spells with the right gear and spell damage increase related mods. But they still have the constraints of running out of mana, needing to stop to cast, having little close-in protection or defense, and no other meaningful means of defense once they've expended mana. Melee have no such constraints and they tend to ultimately gain an upper hand over casters by the time a game has been patched and expanded a bit, and especially after superior linear progressions of gear have been introduced.
It seems I veered pretty far off topic. It's just think I think the OP really is mentioning something that is happening to casters in general in online games... it's not specific to UO.