The solution is to watch the cast bar over the AOE ground indicator. Because the AOE ground indicators can be so misleading, one should pay attention to the cast bar first. Some AOE indicators flash very briefly at the higher levels, and if you're not out of them before they even appear, you will get hit. And this is regardless of what your latency may be, so it happens to everyone.
Additionally, if you are concerned about latency being a true issue, you can always try a VPN. I use Mudfish, which has a Pay Per Traffic plan over a monthly subscription, so I just load up money onto it and use the VPN as needed. I loaded $10 USD onto it back in December 2018, and I still have over $7 USD left, and I use it pretty much every day. It won't get rid of latency entirely, but it can help reduce it. I went from 130~150ms to about 90ms, so a huge improvement. Obviously, though, if you are on console, this is not a solution. For consoles, I'd recommend changing you DNS settings and hardwiring the console into your router with an Ethernet cable if you are able to get rid of any potential Wi-Fi instability.
For gathering percentages, that's just RNG hard at work. It's frustrating, but that's what it's good at. Make sure that you are using your Mastery abilities to increase your gathering rates on items that you really want to gather. There are 3 basic kinds that are all learned by level 10:
- Field Mastery I: increases gathering rate by 5%; 50 GP
- Field Mastery II: increases gathering rate by 15%; 100 GP
- Field Mastery III: increases gathering rate by 50%; 250 GP
Make sure to stock up on cordials to use to replenish your GP faster. You can either craft them (level 50 ALC), or buy them from your Grand Company with Seals. Hi-cordials can be bought for Yellow Scrips, and replenish 400 GP. While they have long cooldowns (4~5 mins), they're a valuable thing to have.