None of the NM dungeons you did were hard because it starts you off at Tier 1 and slowly gives you higher tiers as they drop, but the jump isn't much. Tier 1 NM is probably easier than normal outside enemies. You have to craft higher tiers if you're not finding any challenge. That's the purpose, finding a higher tier that challenges you, or even proves too much of a challenge and working your way up to that then beyond. WT3 max is Tier 20, so build a 16-20 and try it out. If you run 5 of those and none of them are difficult for you, then go do the capstone dungeon and move to WT4.
I've done more than tier 1. I think 8-10 range? Don't remember.