How to activate the dwarven item in Raldbthar

It is somewhat known that most areas have some sort of scaling mechanic. If you have a quest that is quite difficult it could be a number of things:

• The game's difficulty setting
• The level of the skills you are using affecting how well you can do combat
• the scaling, when combined with the difficulty setting, has made the enemies much too difficult
• The equipment you are currently using
• The combat strategy you have been using has been inefficient and it hasnt been a problem until now

Try setting the difficulty lower and see how low it needs to go before it becomes managable. It may just be that the scaling for that quest is off.

As far as I remember from my "get all the words" run, no. There's one dungeon with the word wall easily missable because the wall is actually outside the dungeon itself but it's a secondary quest linked dungeon. The exit is actually on a ledge you cannot really reach above the entrance. The wall is too far away from the exit for you to get the music telling you it's nearby so it's easy to just go away from there without learning the world.

Also, during the main quest, one dungeon, the one where you need to use a shout to pass some timed doors, the word wall is kinda in the middle of the dungeon a little out of the way but if you really are into exploring most of the places you visit, you shouldn't miss it.

All in all, the only word you can really miss is the one on a dungeon in the main quest which is explicitly described as impossible to reach through normal means but the word is right in your face on the way. You cannot revisit the place later.