Easiest trial DD nowadays: Stamina Arcanist. Option #2: Stamina Arcanist. Option #3: Heavy attack sorc. Option #4: Magicka templar. Option #5: Not a necro.

Coral Riptide: That's a big fat no, if you want things easy.
Ansuul: It's an easy to use set, but I tried it on Arcanist and it's "not bad, not great".

Do not pair two trial sets. They both have the Minor Slayer buff, which doesn't stack. In fact, you don't need trial sets at all. I use the following on my Arcanist:

5x Deadly Strike
5x Pillar of Nirn
1x Velothi Ur
1x Slimecraw
1x Maelstrom Inferno back bar

I parse 90K+ with that on a trial dummy and I consistently do in the range of 13% to 18% of boss damage in non hard mode, non progression group trials. Aside from rotation (as with every class) Arcanist is all about positioning. If you can keep the beam up and have at least the boss and one add in the crosshairs at all times, you'll do above average damage, like me. It's very hard for the average player to come close to an Arcanist, now that we are post the lightning heavy attack nerf. Superior players will still beat you with any class.

There's an easy rotation Arcanist on NinjaPulls web site, which uses a flame staff front bar and Blackrose dual-wield daggers on the back bar. I have not had my best parses with that approach and the build uses Exhausting Fatecarver. I prefer to have some defense. In some trial content you need to self heal and a shield can't hurt. I, therefore, prefer Pragmatic Fatecarver. My rotation is:

Pre buff: Quick Cloak, Recuperative Treatise, Resolving Vigor

Back bar (flame staff): Fulminating Rune, Elemantal Blockade
Front bar (dw): Barbed Trap (for bosses), Cephaliarc's Flail x 2, Pragmatic Fatecarver, Cephaliarc's Flail x 2, Pragmatic Fatecarver
Back bar: Elemental Blockade, Recuperative Treatise
Front bar: Cephaliarc's Flail x 2, Pragmatic Fatecarver, Quick Cloak and back to the start

Finally what people look for to get you into a Craglorn vet trial PUG run is not your DPS. It's a prior Conqueror achievement for the trial in question, e.g. prior completion on vet. The best way to get that is via a guild that organises training runs and explains the mechanics. It's knowledge of the mechanics people look for above all, not DPS. This is especially important for places like Dreadsail Reef, where any player can easily end up wiping the whole group on the first boss. That said, vet Hel Ra and the other Craglorn trials are cakewalks.