need some advice tankingFollow

i'm a lv50 PLD and im having problems holding agro
im a full vit + mind build
my gear gives me +54 emity
Most of the cases i'll cast
Sentinel - > Flash -> normal attack till TP gets to 500 -> war drum
but every single fight turns out that most of the mobs are attacking others
before I even get war drum on
Dps casts their AoEs or attacks while im trying to get the 500 TP
so mobs goes away before war drum and never comes back
and delay's my wardrum because the mobs are mostly gone when i built up 500 TP
and I cant flash it again till the next 30 second..which is really long...
provoke's only doing single target..and it wasnt even effective...
By the time i get to cast flash again the mobs are now stuck to the dps due to their continuous attack

I asked some other PLDs and they said healing gives emity as well ,the more I heal the more emity
but ...my MP is limited.. i cant keep healing the whole fight and the mp regen skills are very limited
I've even try casting heals during the situation in top , the mobs are not coming back :/

I got stuck there...i mean yes i can probably get more +emity items , but it doesn't seems like it would solve the problem
can anyone tell me where I went wrong ? am i using the wrong skills or something ? coz i'm totally lost