This is purely from a lazy, casual player perspective so keep that in mind.
Bar swapping is the single most annoying combat mechanic in this game, hence all my builds are single bar builds. Don't get me wrong... I've optimised those to do a decent 25-30k dps or sometimes a bit more, and is still usually the top dps on my pug runs, and survive pretty well in pvp the few times i go there (I don't do much trials). I would like to make use of both bars but it's just way too clunky.
Why I don't like bar swapping
For me bar swapping mostly becomes a dps loss, when I constantly end up on the wrong bar, casting the wrong skills, wasting resources and precious time. In pvp bar swapping often becomes my main cause of death for the exact same reason, which is why I focus on doing well rounded single bar builds.
If feels like a chore to constantly swap to keep up buffs, dots etc during longer fights. Yes! I'm a lazy player...
My typical 1 bar build looks like this.
1. DPS skill
2. varies. (heal, extra dot, passive whatnot)
3. area skill (brawler, endless hail, wall of elements)
4. Buff/dot
5. passive (bound armaments, camouflaged hunter etc)
U. Ultimate
P. Potion is usually for longer lasting buff/resource gain. only used in boss fights.
What do I use my second bar for?
* Skills i'm leveling up, switching to this bar when handing in quests etc.
* Utility out of combat skills like rapid manouver for faster travel.
* Unlimited duration elemental susceptibility, pre boss fight so i don't have to switch over again.
* Some support in case of emergency (group heal, etc)
What I wish for, or quality of life improvements regarding bar swapping
Don't know if some of these are doable with addons or if they exist already. But there needs to be some improvements to the bar swapping mechanic and here's some suggestions that would make life a bit easier.
* hitting number 1-5 = automatically switches you to bar 1. and casts that skill. hitting number 6-0 = automagically switches you to bar 2 and casts that skill.
* OR ... Use bar swap key as a press toggle, When you hold down swap key, you're on bar 2. When you release you're back to bar 1.
I don't think these changes would add much of a competitive advantage. They are just suggestions on how to make bar swapping less clunky, so you can actually make use of the second bar without too much fumble, and would make rotations a bit easier for less finger nimble players.
Other suggestions or ideas are welcome!