Is it just me or is the problem being discussed largely down to a 3rd party program potentially being used to auto interrupt etc, in which case I would be surprised if TESO was the first MMO to ever not have 3rd party programs detailed in the EULA.
Automation has always been a bannable offense in every AAA MMO, the only question is will this be monitored and bans handed out in a timely fashion?
Visual clues are given for any casting time spell. Not only that there's an option to turn on a message that tells you to dodge / block / interrupt if you target casts a spell, or charges an ability, with the relevant choice being stated (ie. an uninterruptible spell will tell you to dodge rather than interrupt or block).
The only advantages these addons give so far over the base UI is the ability to see buff / debuff timers (which for many spells is easily visible - though not all) and enemy resource pools (which I agree should be limited, but ZOS disagree and it's their design choice).
In the end though while it does have it's benefits very few people will use them in a beneficial or informed manner. Most people won't take advantage of the additional information or will badly attempt to do so. Paying attention and teamwork will generally be more beneficial than the additional information, especially as player numbers increase and overall strategy plays a larger role than individual ability.