cleric skill combo's ?

using the seal on anything but bosses and other players in pvp will only hurt you.

that combo is, basically, all we got. we have only a few attack skills that are useful and only 3 can be spammed. so yeah, you're killing as fast as you can if you maxed your metal mastery/those 3 attacks.

barbs?

elemental debuff > thunderball > cyclone > wield thunder > cyclone > tempest > cyclone > etc, until you either get bored or he finally dies.

maybe if you're desperate for a fast combo, because that's part of the 10 second rule - kill them fast - you can use cyclone > siren's kiss > cyclone. though nobody uses the skill, it cast very fast, and can be strung together very quickly. that's a good chunk of damage in a very short amount of time.

Based on my PvP and TW experience, the most successful combo I've had against Barbs and BMs is: Plume Shell > Chromatic Seal > Elemental Seal > Double Spark (hopefully your sparked) Cyclone > Weld Thunder > Cyclone

Honestly, in pvp it takes two different paths.

1 v 1 pvp. Whether pk, in the cube, DT, or some strange off the wall TW encounter, it's you against 1 other person. If you are the aggressor:

Heavy and LA: Wield Lightning as starter. If you tick the charm, he's weak. If targeting a stun class, might want to sleep them for safety's sake and then spark wield to kill them if you feel lucky, or just wield/cyclone. Remember, if you don't kill them before the charm recharges, it ruins your whole damage output. And everytime I did a sleep/spark/wield/cyclone combo after ticking the charm, they recharged right as it hit with cyclone. So either have -9% or better channeling boost gear, or try a shorter combo.

If you don't tick the charm, and they are around 60% health, then sleep, debuff, tempest. Kills them guaranteed.

If not enough sparks and fighting melee, go with sleep, debuff, max distance, plume shell, thunderball, cyclone, wield, cyclone. You can change this around as needed for how safe you feel, and whether you know how good the target is. Thunderball is used to tick the charm and set up some dmg to hit during that 10 sec recharg. You should get 60% of the DoT to hit during this time. I go with cyclone first usually because once they wake up, they tend to start using healing pots. And needing to use plumeshot because you don't have metal spell only combo does not make it easy to kill them. Maybe against LA, but not heavy armor. I needed the cyclone/wield/cyclone when I was soloing barbs within 5 lvls of mine. Lower and I could skip to wield/cyclone only.

For arcane: Razor if aggressor as opener, then sleep. When asleep they can't stun/sleep/order their pet to kill you. Again, if charm ticks, just spark and razor them. Follow up with plume if something keeps them alive. Usually that only happens if you have a large dmg range, and the first one hits high while the second hits low. It's why smaller range makes it much easier to kill in PvP, as you know which combo to do. If they don't have lvl enough to use their condition spells on you, then just save the sparks for a better target.

For TW/organized:

It changes often depending on how well/bad the match is going for you, if you're a small portion keeping the enemy occupied during your guild's assault, if you are the assault team, etc. You'll be switching between different roles constantly, but aside from 1v1 tactics, you will need to assist as needed.

This means freezing/sleeping appropriate targets. Freeze enemy cats or runners, sleep enemy foxes heading to your cats. Add heals to cats if it is needed. If an opportunity to aoe enemy casters trying to kill one of your cats, blast off with a razor feather before joining the healing defense. Killing the dmg on your cat will add more health than 2 IBs anyways.

For more than 1 against just you:

Spark, Cyclone/Plumeshot/Cyclone. If lvl 100, add in Elven Boon as often as possible. Faster casts means higher DPS, as you get that weapon boost hitting more times than higher casts. Aim for light/arcane as much as possible, kill what is in your way to make a hole, and run the heck through it. This method got me out of 7 high lvls surrounding me in DT. Killed 3, chased a 4th and made it out alive. Barely, but it works. Spark makes the best pve combo work in pvp as well.

For PvE: Cyclone/plumeshot/Cyclone/Plumeshot/etc. These are the only skills you need against 1 mob, Wield has terrible DPS for full mag or near full mag. Only people I can see using it are full vits, and even they will eventually get better dps from this set. 30% metal debuff from demon wield might make it nice, but the extra time before they are slowed might mean you take the same or more dmg for spending more mana than normal. Bonus dmg is junk for non-spark skills the higher you lvl. Just compare your base mag and weapon dmg compared to the bonus dmg to get an idea of what impact it really does have.

what's the usefulness of elven boon? i'm yet to see a purpose for it.

Elven Boon, crappy bonus dmg. But as has been posted often, bonus dmg is junk dmg the higher up you go. It's nice, but can that bonus dmg equal out to 33% of your bas mag + 1111? That is what it would have to do in order to have the same DPS as Elven Boon. Seal and heal are just nice extras that are just kinda nice. Because before even getting my +4 Requiem equipped, my base mag is able to deal more DPS with EB than a demon Cyclone even.

EDIT: Should have added, not to try killing a celestial barbarian when you have not made it to the same stage. Doesn't work too well, but I ticked his charm