If the enemies have +Acc or +ToHit built in, or use powers that grant either, then you need proportionately higher defense to floor them.
Also, it's my understanding that higher rank enemies (Lt, Boss, EB, AV) have a higher floor for their hit chance. Your best bet is to read Arcanaville's guide to defense, and if you have questions or need clarification, ask her, either here (if she shos up) or send her a PM.
@Roderick
Quote:
+Acc does NOT affect the soft cap in any way.|
Originally Posted by Roderick
If the enemies have +Acc or +ToHit built in, or use powers that grant either, then you need proportionately higher defense to floor them.
|
To answer the original question, 45% defense is the soft cap for all enemies up to +5. +6 (and above) enemies start getting tohit bonuses against you, and +tohit does affect how much defense you need for softcap.
While 45% defense is still the soft cap for +5s, enemies which are higher level than you, or higher rank than minion have their hit chance floored at something higher than 5%.
Essentially, enemies get +10% acc for every level they have over you (until +6, where they get +tohit instead of +acc). Lieutenants get +15% for being lieutenants. Bosses, EBs, and Snipers get +30%. Monsters, GMs, and AVs get +50%. The accuracy provided by the critter's level difference is multiplied by the accuracy provided by their rank (and also multiplied by the accuracy of the power they're using, but for simplicity, assume they're using a 1.0 acc power).
As such, a +5 AV still gets his hit chance floored when you have 45% defense, but their hit chance will be 1.5 (level difference) * 1.5 (AV rank) * 0.05 (floored from your defense) = 0.1125 = 11.25% chance to hit, rather than 5% chance. On the other hand, a +0 minion is 1.0 * 1.0 * 0.05 = 0.05 = 5%
Edit: Paragonwiki's page on Attack Mechanics is a very good resource for this.
http://www.fimfiction.net/story/36641/My-Little-Exalt
Quote:
Not quite accurate. The hit chance floor operates independant of accuracy. The higher a critter's accuracy with a given power, the higher its odds of hitting you after you "floor" its hit calculation. The way this works out is that the minimum average hit rate of a critter due to defense and debuffs is 1/10th of its standard hit rate. This assumes no toHit buffs for the critter and no defense debuffs for you - as you say, those do raise how much defense is needed to "floor" critters.|
Originally Posted by Roderick
If the enemies have +Acc or +ToHit built in, or use powers that grant either, then you need proportionately higher defense to floor them.
|
Quote:
| Also, it's my understanding that higher rank enemies (Lt, Boss, EB, AV) have a higher floor for their hit chance. |
To answer the original question, no, the 45% defense "soft cap" is not just for even level mobs. It used to be until I7. Before that LTs and bosses and over-level mobs of all ranks got the equivalent of +toHit against player characters. In I7 this was changed to +ACC. This made defense powers scale against foe ranks in a way analogous to the way resist powers do, at least on average, and in the absence of +toHit/-defense.
Blue
American Steele: 50 BS/Inv
Nightfall: 50 DDD
Sable Slayer: 50 DM/Rgn
Fortune's Shadow: 50 Dark/Psi
WinterStrike: 47 Ice/Dev
Quantum Well: 43 Inv/EM
Twilit Destiny: 43 MA/DA
Red
Shadowslip: 50 DDC
Final Rest: 50 MA/Rgn
Abyssal Frost: 50 Ice/Dark
Golden Ember: 50 SM/FA
The very simple (and simplified) story on this is:
Your chance to hit things is basically Acc x (ToHit - Defense)
However, the part inside the parenthesis obeys a 5% minimum. *Most* critters have a base 50% tohit, and additional accuracy factors based on their rank and their level relative to you. Clearly, the accuracy factors don't matter to the question of "how much defense is useful" because the inside part obeys a 5% floor. So past 45%, you're driving that value below 5%, and the game makes you obey the floor.
Three big exceptions:
1. Tohit buffs. Some critters possess tactics-like powers, build up, or other tohit buffs. They will obviously increase Tohit and having more defense would help against them.
2. Pets and Turrets. Pets and Turrets were not changed in Issue 7 to base 50% tohit; they still have 75% chance to hit. It takes 70% defense to floor those guys. Since few players are perma-eluded when they first face Frostfire, many players don't notice this initially (many players never learn this at all). But they might wonder why Malta turrets seem exceptionally lucky bastards.
3. +6s. If you are fighting things that are 6 levels higher than you or more, they start to get additional tohit buffs against you, not just accuracy buffs (like +1s through +5s get). If you are fighting +6s all the time, more defense would help (5% per level higher initially: if you are fighting things way higher than that, you don't need my help).
And, as others have mentioned, anything with high accuracy cannot be "floored" to 5%, because if the inside is floored to 5%, the total can get no lower than Acc * 5%. The higher the accuracy of the attacker, the higher his lowest possible tohit against you can possibly get. However, the floor is always (for reasonable numbers) 10% of his original tohit against you without defense. Think of it as a similar situation to the 90% resistance cap.
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Thanks to everyone for all the replies.
I think I understand it much better now.
Since I do not plan on fighting things higher than +5 levels the 45% defense I have should work out fine (except when those lucky shots get through all at the same time and I get flattened like a pancake 
)
Arc 52555: Tower of Darkness
Arc 139668: Bob's Crazy Car Dealership
I know that 45% is softcap and above that is basically only good to fend off defense debuffs.
What I want clarification around is if 45% is just for even level mobs?
If the minions are say +1 can I get them still down to just 5% chance to hit me or will they have that 1.1 modifier to of set no matter what?
Thanks.
Arc 52555: Tower of Darkness
Arc 139668: Bob's Crazy Car Dealership