Wanted to post one quick comment on Lucks and "flooring" a boss.
The concept of "flooring" is going to change soon, if you want the exact details read Arcana's guide to Defense. Here's the short version however.
Old
Bosses had their innate (boss) accuracy and level bonus *before* defense was factored into the formula. This made them very, very accurate but it was still possible to eventually floor them down to 5%
New
The innate (boss) accuracy as well as the level bonus will be factored in *after* defense. While it will be easier to minimize their to hit chance, you will no longer be able to make a boss at 5%.
To keep it simple I will use a +0 boss and round numbers off. "Boss Bonus" will be defined as 30% (or 1.3 multiplier)
Before
50% ACC * "Boss Bonus" = 50 * 1.3 = 65% - 60 Def = 5% ToHit (aka Floor)
After
50% Acc - 45 Def = 5% * "Boss Bonus" = 5% * 1.3 = 6.5%
In short, it takes less Def to minimize a boss' chance to hit, but you can never actually achieve the 5% minimum anymore. In your question above, you asked how much for a +3 boss. The answer is "45% Def" (or 2 Lucks will do it) but the end result is the boss will still have higher than 5% chance to hit you.
I request a guide to inspirations. How many luckies does it take to floor a +3 boss? How well do various types of inspirations stack? If I can regenerate 25% endurance in fifteen seconds, is that 25% endurance buff as good as a 25% base damage buff that lasts one minute? How are these questions affected by the fact I am a Spines/Regen scrapper? It seems, as with any other buff, I need to know my caps (if any). These are just some sample questions. Ok, some of the answers may be obvious, but I believe there are real subtleties here. Please post your wisdom.