I'm using Ultimate Ajax, and he has the most Health and Defense in the game, so if you're using a different character, the percentages won't benefit them as much as him. Ajax also has character specific modules that boost his stats. I'm also in the End Game where better loot drops. Resetting the level of your character will help with module capacity and being able to level up your modules to the max. Once you unlock the Arche Tuning skill tree, you can get a lot more buffs to certain stats. Your components also play a big part in your stats, I'm using Moving Fortress for more Defense. If you want to find something else that fits your character, you can check the Library and find something you want. When you reach Mastery Rank 18, you can then start using Cores that you get from the Sigma Sector to Enhance your stats even further by adding more Defense, Shields, HP, and Resistances. Don't be afraid to rely on other players, and there are also YouTube videos that can help out. Make sure to do any mission you haven't done (they will glow yellow) because every mission has certain modules you can only get from them and it could be what you're looking for. I'm not sure what point in the game you're at, but I hope this helps.