I think everyone in his RAID career have experienced this at least once.
I've been starting experiencing this way back in faction wars, all i did was just wait the buff to expire.
Sometimes, there, you just can't and you need to start over because your team has speed, stuns, slowdowns opponents and such in most parts of champions skills kit you have in that moment.
Speaking about arena, is pretty much what people have been said here:
Opponent geared with tons of defense and resistance to last as much as making the challenger end the battle with a loss. (get the best out of bad stuff, on your next refresh you will have at least 1 easier battle due to that loss. Tons of players purposely queuing up a single champ 1k player power with a like 200 to 400ish Team power and purposely insant end battle to "respect" the message the presumed troll is sending to challengers.
Remember, not ALL single teamed Paragons have that much RESIST and\or Stoneskin gear.
Decide by yourself to higher accuracy on best champs that are high arena tier and very good in all other places too, bring in a your best champ with relative stats to counter this scenario or just ignore this battle and go next one in the list.
And yes, you need to experience this (even more than 1 time) to acknowledge what you should do in the process.
Hope those advices will help you reflecting and read champions skills even more than 3 times and even over time.
Ended up myself in those scenarios when i thought i was 100% sure about what given skill does, turned out i was wrong.
This is pretty much to be consider a life lesson from Plarium if you think about it a little bit :)