Question about Dominating Blow and Sentinels of Purity as a Guardian

Which one of these minions do you think deal more damage overall?

I just got a helm with:
-3 level to socketed minion gems
-socketed gems are supported by lvl 16 minion damage

As far as I can see, dominating blow minions tend to be up in their max number (9-12) fairly quickly while there is often just 1-2 sentinel around at the same time. (I know it all depends on how good I kill.)

What do you think would be a better idea of socketing into this helm, either my Dominating blow with:
-multistrike support
-faster attacks support
-melee splash support

or my Sentinels with:
-splash support
-melee phyisical damage
-maim support

I also need to consider that dominating blow would work better in a 5 link chest with an extra support gem as this skill is also where my damage comes from. Thing is my minions do most of the killing for me, I am often going around looting or just running for my life while minions deal with the boss.

This is why I thought that me gimping my dps a bit and putting Dominating blow in a 4 socket helm instead of my 5 socket chest wouldnt hurt me that much.

Im play this build too and have another question:
im 6k HP, 9600armor. Its build described as "very tanky" but im have oneshots everytime and everywhere after start playing ~14tier map and above.
Its can be boss, regular pack, anything. Looks not "very tanky" at all.
Very often 1ms oneshoot deaths in heists ~ 82-83lvl when open door when escape. Can pass 10 big paks and next pack oneshot in miluseconds, just instant.
Its that league work? My build wrong? Its must be 10k hp and 20k armor? ))