Currently we're still in progress of helping people level up to Veteran Rank 10 & Above for Trials. We're aware you can enter trials at lower vet level, but the damage is not that great. Those of us @ vet 10 & above have been running Trials with Manpoints' guild, to get the experience and learn the fights, which Manpoints has been wonderful with and working VERY hard to help people! Good progression is being made!
It is my experience that veteran levels matter less than good class knowledge, rank IV morphed skills, and consumables. Obviously you want your trials group to have every advantage that is easily possible, so VR12 helps but being a player who consistently works to test powers and improve their build and skill outside of trial content is huge.
Some general advice:
Grab a tool like recount and check your sustained DPS in a group setting. 500 is about average for single target. Perfected builds with consumables and high end gear should pull closer to 800.
Try to find a 4-man group and take on some of the craglorn dungeons and veteran instances. Start with the easier stuff like the VR5 banished cells and the VR10 wayrest sewers, then try your hand at the rest. There are some good guides at Dulfy.net to let you know about boss mechanics.
Level provisioning and alchemy and make yourself some consumables (+stats food and +dps potions). The amount by which these boost a character is huge.
For the most difficult challenge, take a group to Shada's tear without researching the mini-dungeon. You may need about two hours for this :P Any group serious about fully completing the trials, particularly Hel Ra, should be able to beat the final boss of Shada's Tear.