People take Iron Reflexes because it's a safe way to build decently without much input and because it used to be the only way to really build. With that said I think it's now the worse of the 2 paths. They also take it because they want Unwavering Stance, and if you get US then why not take IR, I mean, you can't evade anyway so might as well convert evasion to armor so you can equip different types of armor and Grace isn't wasted.
Evasion isn't "streaky". It uses a system that works kinda like adding a number based on accuracy vs evasion into a pool, and everytime the pool hits 100, the hits connects and 100 is substracted. If your evasion is low, the hit is like 90, the starting number is random, let's say 40, so first hit you're at 130, you get hit, you're now at 30, 2nd hit you're at 120, you get hit, now at 20, 3rd hit you get hit now at 10, 4th hit you get hit, now at 0, 5hit you dodge. There's no randomness to it other than the initial hit and what value you start at. Now against a large amount of mobs, you can get hit by every mob on first hit and take large bursts, so that part is fairly streaky, however if you evasion is high, they will all miss their 2nd hit. So you only need enough to survive the bursts. With the right amount of evasion, block(separate roll), acrobatics(dodge which is like block other than you can't get stunned, separate roll), enfeeble(accuracy reduction, up to 80% iirc?) and blind(75%chance to miss), it means you literally get hit once in 100+hits by a given mob, assuming it's properly debuffed. It will never hit twice in a row(unless it's a spell then you're kinda fucked).
The only thing to understand about Evasion is first, you need health, because you will get hit sometimes, and you need to be able to survive, nothing really special there, it's basically the same shit as armor. The second is you need to stack all the various sources of avoidance to make sure you keep a high lvl. Evasion alone sucks, Evasion+acro sucks, Eva+acro+block is alright but still kinda sucks, Eva+acro+block+blind is great, add Enfeeble which both reduces accuracy AND damage and you're golden. Don't even need to lvl Enfeeble(which is int based so annoying to use if not dagger), but a quality gem helps a lot.
On the other hand, Armor sucks everytime you fight something that has high damage. Armor blocks based on the damage done, not as an absolute reduction, and it blocks less the bigger the hit is. That means that for armor to actually matter, you need to bump it very high before the big hits. If you know the big hits are coming and Granite of Ironskin+Molten Shell+End charges, then you won't take a whole lot of dmg. If you don't do that shit, armor alone is fucking useless. Similar to Evasion really, you need all the tools combined for the stat to actually matter.
