According to this website, the effective HP provided by adding deflect is lower compared to adding an equivalent amount of HP (e.g. adding 1000 deflect provides <4000 effective HP), unless you meet one or more of the following criteria:
1. 75%-85% deflection severity like TR
2. Very high base deflection chance (>~30% if sev is 60%)
3. Very high base HP (>~200k if sev is 60%)
Not to mention deflect doesn't help against piercing dmg. Aside from proccing deflect boons, why do people prefer deflect?
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The higher deflect the greater the chanse is to cut many attacks into a smaller amount of total damage hence surviving.
That a deflected attack also cuts the duration of a deflected cc attack also increases the value or having high deflect.
Same goes if you are attacked by several opponents at same time you can not build enough hp but having 50% + in deflect will most likely cut the damage of half the attack by at least 50% that is taking 25% less damage in total.
Adding to this there are several boons and items that trigger on a succesfull deflect that either deals damage or heal yourself also makes a high deflect more useful.
if you are controlled longer the extra hit points you may have gained will be whittled away anyways ..
that being said i can run at around 50% deflect and still have ~ 250 k hitpoints ... with very few rank 13s in defensive slots at the moment
changing the guild boon to give boost on potions drinking may help as well if it is not bugged again with pvp poition
you may be able to squeeze more hit points by using only mount insignia selectively with them the (+800 hitpoint ones )
Like you said, stacking deflect makes sense only if you have a lot of HP. All of these burst dmg GFs,TRs etc, you always want ~200k HP and around 50% deflect next to that.
I usually run around 230k HP + 16k (23k with ring/boon procs) deflect and can easily 1v1 GFs with that, but only cause even if they hit me for half of my HP or more, theres a big chance that their next attack will be deflected,so I have time to either debuff them more or heal up if possible.
I think that stacking just HP wouldnt do the trick, unless you are a GF or OP.
Same goes for deflect, you cant stack it without lots of HP either, there has to be balance between those two.
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If you compared two builds, one with deflect and the other with an equivalent amount of HP, ignoring the CC reduction effect for the moment, they should theoretically die at the same time when the same amount of damage is inflicted upon them. In fact, HP allows you to survive more consistently against high burst hits because one with a deflect build may fail to deflect multiple times in a row with a non-trivial probability.
People above have mentioned that having high deflection helps you survive better when you're low in HP, which is true obviously. But you're neglecting the fact that you get low faster when you favor deflect over HP in the first place; the math just doesn't lie.
All in all, I do think that the CC duration reduction and reflect dmg boons make deflect an overall preferable option in PvP for many. However, it's important to note that HP does outperform deflect, at least in terms of providing an effective HP pool, more than just marginally.
Mod 12.5 PvP Power/Crit/Arp Optimization
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not to say you dont need at least a moderate amount even with 30% life steal
pally so broken in pvp at the moment players dealing no damage to it and the class then can heal for like 200k in one shot despite healing depression