The new Lancer is out and I've been spamming games on him. I've had a ton of fun, and I'd like to share my thoughts!
Dawnhammer: Small AOE hammersmash at short range.
Reforge: Powerful longrange heal that scales with missing health (low hp targets will heal for a crapload!) The heal always affects Meridian, and weakens in a moderate area on the target of the skill
Boneshatter: Large semicircle AOE slow and damage hammersmash
Solar Strike: Ranged damage Hammer toss that reveals and does additional damage in the epicentre
Zenith: Activate to grant AOE shields and self-unstoppable
I'm not sure if he's OP, but his numbers are certainly bonkers. He has insanely high contributions because of his large AOE damage, shields, and heals. He can also burst Reforge's up to 50 heals with AOE weaken, plus 15 shields from Zenith for an absolutely insane 65 healshields, while still affecting himself with the same heal and shield, and weaken the enemy. This support combo is on a very low cooldown, and very often takes enemies by surprise with Meridian being so new still. His damage numbers are modest, sitting in the mid twenties, but even his shortrange small AOE Dawnhammer is deceptively powerful if it hits more than one enemy. In fact, all of his damage abilities are pretty respectable AOEs, and none of them can be bodyblocked.
I've found success by modding for the maximum burst heals, and playing like a frontline with great survivability spells in his unstoppable ult and his heal. His base HP is enormous, however note that this requires the Meridian to position very aggressively, and will need a secondary support to contribute to his efforts. Orion is a great option, Khita is powerful, and I think most supports work just fine with him.
The reason that I hesitate to label him "OP" (even though he will likely nee nerfs) is because at the end of the day he is still a melee support with no dash, and no way to consistently heal turn after turn. His heal, and even his ult, do have significant downtimes, or situations where they are not useful (if allies are already full hp for example). This means that during his downturns, Meridian needs to be contributing in-your-face-damage, which puts him at risk, or he's just an extra body soaking damage. This means that without a second support on the team, Meridian is a high risk pick.
Meridian can be kited very effectively. He doesn't have a dash to gapclose, and if his team is not locking down targets for Meridian to Hammer, Meridian will find himself 'stranded' like a bad frontliner a lot of the time. And again, it's very important that Meridian is using his huge healthpool and large AOEs to soak and return damage on the frontline, or else he is not an effective lancer.