Warning Math Ahead: For TLDR scroll down...or past.
45% defense when solo, facing a single enemy: (scenario: defeated everything but the remaining AV).
given:
enemy +3/AV
all enemies have = 0.5 BaseHitChance
enemy's power inherent Acc = 1.0
enemy RankAcc = 1.5
enemy LevelAcc = 1.3
so: Every attack from the enemy can hit only you, since there are zero other team members.
Estimated Probability of getting hit (when you have 45% defense):
Enemy AccMod = (enemy's power inherent Acc) X (enemy RankAcc) X (enemy LevelAcc)
= 1 x 1.5 x 1.3 (note: these values taken from 'Attack Mechanics' wiki page).
= 1.95
= 0.95 due to clamping
New Enemy ChanceToHit = enemy AccMod x (enemy BaseHitChance - player's defense%)
= 0.95 x (0.50 - 0.45)
= 0.95 x (0.05)
= 0.0475
= 4.75%
Now the fun part:
Estimated Probability of toon getting hit in consecutive attacks: Note: All attacks enemy has are 0.95 AccMod. (for giggles because if enemy's inherent Acc for various attacks is different, so everything changes).*
...it defaults to lowest ChanceToHit attack... the one with lowest inherent power Acc.
1st attack = 0.0475 = 4.75%
2nd = 0.0475 x 0.0475 = 0.0022 = 0.22%
3rd = 0.0475 x 0.0475 x 0.0475 = 0.0001 = 0.01%
4th = 0.000005 = 0.0005%
5th = 0.0000002 = 0.00002%
6th = 0.00000001 = 0.000001%
etc. it's basically all enemy whiffs.
The probability changes with different enemy powers if they (each) have a different inherent Acc.
Now lets take a step after and see what streakbreaker does... because this is how the game works:
https://archive.paragonwiki.com/wiki/Attack_Mechanics#The_Streak_Breaker
"The system does not track each power individually; instead it tracks every miss you (the ENEMY) makes in a row, regardless of power (or target)."*
when solo... same +3/AV and 45% defense conditions as above.
For any enemy whose "New Enemy ChanceToHit = 0.0475" is between 0 to 0.2 from chart above... = 100 consecutive misses allowed... then streakbreaker guarantees a hit on hit #101.*
So the probability of getting consecutively hit with is now looking like this due to streakbreaker:
*Remember this example is for solo play. (when playing with a team, everything changes, because enemy counts misses and adds them up from different team members).
1st attack = 0.0475 = 4.75% (this rounds to 5% which is always the minimum ChanceToHit).
2nd = 0.0475 x 0.0475 = 0.0022 = 0.22%
3rd = 0.0475 x 0.0475 x 0.0475 = 0.0001 = 0.01%
4th = 0.000005 = 0.0005%
...
*101st = 1.00 = 100%.
Every 101 times enemy attack will hit. The chances of attack #1, #2, #3, #4 through #100 still may happen, but the chances happening are very very low.
100 misses and then get hit. Rinse and repeat.
That 45% defense page from the wiki does not hold water. I showed the only situation where it may work (that I can come up with) in the example above... solo play with enemy having only same inherent Acc in every attack power.