I'll share my toughts on tanks in your version of the game . Firstly I think its awesome you guys are changing and adding skills so we can have better class balance. I'll talk mostly about DA since I have most knowledge about this tank class.
So everyone knows that tanks are the useless classes in interlude. Very few people will take a tank in their cp in this chronicle because people want fast level/fast gear - for which mage/archer/melee(destro) groups are standart. This changes a lot in chronicles like epilogue/h5 - there they are very good classes and you can even say OP, but why.
DA is really powerful pvp class if geared in interlude - 78-79 HK with sword, bow, mage acu wep and say tallum can destroy every other class in oly:
-fighter classes like gladiator, dagger, destros get a lot of dmg back with shield of revenge, also shield slam duration is really long
-wont even talk about archers(deflect arrow)
-shackle or hamstring a mage and its dead with the panther (if you change the target on you, so the panther stays alive)
- summoners are tricky, but if some shield stuns land you can deal with them
and so on.
Lets take a look at the skills you add:
- shield deflect magic - really strong skill for pvp vs mages
- shield strike - another pvp ability which is like Judgement/Tribunal
- add the skills on the panther - cancel, decrease dark resistance and the damage ability - which are mainly used in pvp/oly
- burning rage - I'm not sure about the effectiveness of this skill
- the active abilities from Vanguard - which take a lot of mana and are not reliable farming tools
So the point I'm making is you are making tanks stronger in oly(in which they already are really strong), but for the two more interesting aspects of the game - their pve and mass pvp potential - still the same and which is the real problem with the class.
So what makes the tanks strong in pve/mass pvp in latter chronicles-
1) banish seraph ability - its really bad in interlude (unlike epilogue+). If you reduce mana cost and increase land rate DA/SK will have a reliable farming tool in higher levels. Same with banish undead for pala/tk. Remove the 5 soul ore that it is needed.
2)The only useful skill in Vanguard is the buff - https://l2db.info/high-five/skills/956-Boost-Morale, which stays after you transform back.
3)Combat aura- strong buff for the whole party https://l2db.info/high-five/skills/982-Combat-Aura/2
4)DA shares buffs with panther
and so on - you can use your imagination.
So I suggest you to boost their pve/mass pvp/party usefulness instead of their oly pvp potential. Because as it is now, a bd or a sws can do everything that tanks can, but +dances/songs. There are plenty of ways to do this and I hope you will look into this for the x25.