No, multiple instances of the burning ground damage from Fire Trap will NOT stack.
Only different sources of burning damage can stack. For example, an Ignite debuff from a spell's critical hit and the Fire Trap ground burn will stack.
When 2 of the same burning sources are present the highest damage source will take effect. Multiple effects can still apply, like 2 Ignites on one mob, but only the highest damage one will actually deal damage.
Once the highest damage effect ends, if another instance of that effect was applied and still has duration left, it will then do what damage it has left. This goes for Righteous Fire, Ignite, and Fire Trap's ground burn effect. Searing Bond, a recently added skill, is an exception and the beams can stack with itself.
This is why you should try to spread out Fire traps a little bit whenever possible.
Posted by Mark_GGG, PoE developer and creator of the games skills and their mechanics.
...Ignite, RF, ground fire and now Searing Bond are all separate
sources of burning damage, and all stack. Ignite, RF and ground fire
do not stack with themselves (only the highest of each takes effect at
a time), but do with each other.
Searing bond beams stack.
As of Patch 1.0.5 Searing Bond Beams no longer stack.
Zealot's Oath will not cause Energy Shield to regenerate when using Life Flasks. Flasks recover life rather than regenerating it. Regeneration and Recovery are treated entirely separately despite having similar effects
As a nail in the coffin here's a quote from Mark_GGG, one of the developers:
"Much more interesting for me is, whether it works with fixed amounts,
too. Like the Armour and trinket affixes. Because that could be real
strong. And awesome." - Cazychel
Yes, all life regeneration. Note that flasks and leech, among other
things are not regneration. But anything which says it's life
regeneration will work with ZO
Best Answer
Yes, with 4% HP regen per second, it is very possible to out-regen the chaos damage.
When you get into Cruel and Merciless modes though, you start with -20% and -60% chaos resistance though, so (without chaos resistance) you'll be taking more than 4% HP damage per second.
One way to deal with this is to get Chaos Resistance, but Chaos Resistance is rare and hard to roll on gear (ie. Expensive to get). You can also just get additional %regen to compensate further for the extra damage you are taking. Additional Regen can be obtained throughout the passive tree, through Vitality Aura gem (gives close to 2%) or through certain unique items.
Blood Rage gives you Frenzy Charges, so one of the best items to get to out-regen it is Blood Dance http://pathofexile.gamepedia.com/The_Blood_Dance
These boots will add 1% regen per frenzy charge you have, so you can get 3% regen just by having 3 frenzy charges, which you will almost always have since you get a frenzy charge on kill while Blood Rage is active. You can get up to 7 frenzy charges by passive tree (3) and Act2 Bandits Quest (in Merciless mode, help Kraityn)
Edit: Since the introduction of corrupted items, it is possible to get more than 7 frenzy charges, since you can corrupt certain items (including The Blood Dance) to give +1 frenzy charges as the implicit stat.