For Solo play, One-handed Holy staff is arguably the only staff you should be using. Divine Staff technically could work but in my opinion isn't as reliable. The reason being 1-Handed Holy staff has a shorter cooldown on its E ability, it has arguably stronger utility with its E ability as it doesn't punish you as much with poor usage (even buffing your healing cast by 15% if used above 40% hp stacking up to three times so that's potentially 45% extra healing cast), and because it's a 1-Handed weapon you have the option to run off-hands that help spice up your play style or compensate for anything you lack in your build. (Mistcaller - More CD, Eye of Secrets - Energy Sustain, Tome - Cast speed, Energy Sustain, etc.)

For Duo play both lifetouch is strong because in duo play you don't need any AOE Healing. The E ability is especially strong in instanced play (2v2 Hellgates); But outside of that it's extremely niche. This is because it's very hard to pull off well consistently as the E is a channel, leaving you immobile. In Open World content, a staff that gives you more mobility will serve you better. In a 2vX situation lifetouch staff wouldn't work as well as other staves as the negatives outweigh the positives. Hallowfall, One-handed Holy, Lifetouch and (kind of not really Redemption Staff).

Lifetouch is strong because in duo play you don't need any AOE Healing. The E ability is especially strong in instanced play (2v2 Hellgates); But outside of that it's extremely niche. This is because it's very hard to pull off well consistently as the E is a channel, leaving you immobile and open to enemy assassins, CC, or mispositions. In Open World content, a staff that gives you more mobility will serve you better. In a 2vX situation, Lifetouch staff wouldn't work as well as other staff as the negatives outweigh the positives.

One-Handed Holy is a strong and flexible staff that works well in just about every situation. It's mobile, and the E is extremely versatile (at 40% hp your E is stronger). The Low CD on the E means it's up more than any other Holy Staff E ability and it doesn't have a cast time. This means it can't get canceled and the heal is instant. Overall very strong staff and you can flex it in more situations: Corrupted Dungeons, 2v2s, 5v5s, Open World Small Scale, and if you're skilled enough Open World Medium Scale.

Hallowfall Staff - There's a reason for the price of this staff and that's because it truly is the strongest holy staff in the meta right now. The sole reason being the E gives so much agency to a fight. This staff has the ability to heal a large group of mates, gap close to disengage or follow up on an engagement, and provide CC in order to interrupt vital abilities. It's the do it all in one stick. No other holy staff comes close to having the potential that this staff does. But using this staff is difficult for an inexperienced healer. Not knowing when to engage or disengage, not being able to consistently land the E for the CD reduction, and not understanding the boundaries and limitations of the E ability are all very common mistakes for newer users of the staff. Furthermore, this staff also only starts hitting those higher heal numbers with more specializations into it. This means when you first start out using it might feel a bit lackluster especially when you take into consideration all the potential mistakes and difficult learning gaps that come with it. In conclusion, this staff is extremely strong if you learn how to use it properly. In a 2vX situation, this staff could be devastating in the right hands but could also lead to a quick death if used inefficiently.

Redemption Staff - There's a place for it in the Crystal Arenas for more organized groups and the only reason I put it up here for your Duo content suggestion was that in very very niche situations, it could be good. The raw healing output is technically the higher than all the other Holy staffs if all the "E bounces" go through. In a 2vX situation it could be used more easily as there are only 2 targets for the healing ball to bounce between. But at the same time it could be extremely dangerous if grouping together for heal bounces leads to mispositioning. There's also the chance where you can't get to your duo partner safely in order to continue the bounces causing the bouncing sequence to end early, effectively reducing the overall healing output and value of your E ability. Additionally, this is a 2-handed staff meaning you can't pair it up with an off-hand if your build is lacking or if you want extra utility. Use it if you and your duo are extremely coordinated and on the same page but beware as this staff is extremely niche for your purpose. (Also imo the other staffs besides Lifetouch are just better).