Is Groudon worth leveling up?

There is no better ground specialist, and its a good pseudo grass attacker

However, contrary to how last month's raid were, ground does not typically enjoy the time in the spot light. This is gue to ground moves not being the best statwise. In most cases, when the level of effectiveness on types is the same, ground does not come in first damage wise. For comparison agaisnt dialga, a pokemon weak to both ground and fighting, machamp beats Groudon in DPS in every case aside from when clear weather is present. Groudon is fantastic as a tank, it will likely out TDO the higher DPS compatition, and in PvP is also a beast, but raid wise it does great as a tank counter agaisnt pokemon weak to ground, but other pokemon ith different types out DPS it, groudon however does substantially out tank them. I'd recommend holding offon powering one up for now at least if you have other groudon counters, as you may find a better one sometime soon.

As a grass attacker, it oddly does very well in this respect, being a very good counter to itself if you are carrying solar beam and the other groudon isnt carrying solarbeam. Though there are better options in both of the cases, large numbers of FP venusaur for solar beam sets, and kyogre/gyarados/HC feraligatr for earthquake and fireblast if you have them

In PvP, mudshot makes groudon a monster. the massive EPT mudshot has, its shear stats, and its moves make it have many good match ups. Its weaknesses it can all cover.

I prefer not saying should or should not power up, as its truly up to you whether you want to or not.

Personally I’m stocking up on Groudon candies when precipice blades comes out. Hopefully that is somewhere down the road. According to Gamepress the move is far superior to earthquake. But I’ve powered up three EQ to L30+. But waiting to max one or two with the sig move. Same with Kyogre. But if you don’t have one they have served me well especially with some tier three raids.

You should power it up, as Heatran will still be here when the Hoenn event ends, and Dialga is surely on the horizon. (If they go all out and release the powerful legendaries at the beginning/middle of the gen) Don't power a bunch up however, because, as said before, Precipice Blades is just that much better. That said, you could just TM it to Solar Beam and it wouldn't be a waste after all. (Although it's heavily outclassed DPS wise and is weak to Water)

I'd at least wait until after it leaves raids. You'll have more candy then and could catch an even better one in that time.