ok, this is helpful. Still dont have info like when healing with flash when with martyr etc, and which stats stacking like use trinkets with crit mastery or?
You didn't understand what he wrote so I will explain it to you. When you enter PvP zone/Arena as hpaladin you get the same stats as any other hpaladin no matter what stats you have. The stats for every hpaladin is the same in PvP zones/arenas, everyone gets same amount of crit/haste/mastery etc., so even if you stack your crit to 40%, your crit will be at 20% when you are in pvp. Every other stats will always be the same as well, no matter how much you stack something. If you have 0% haste on your gear, you will have 15% haste in pvp.
You can be in your holy spec when you enter pvp zone and have a full tank or ret gear and your stats will be changed to holy paladin default stats.
Only way to increase these stats is by increasing your item level. So if you have a int/mastery trinket item lvl840 and you get strength/avoidance trinket item lvl 860, the second trinket will be better for you to wear in pvp zone because it gives higher item lvl.
And what spell to use to heal when, I won't answer that because I haven't played in along time so I don't know and this is a thing you learn yourself by playing the game actually.