I am reposting an idea of mine from a different post here.
Personally I think that the Troll Singer would be interesting as more of a half-caster. Give the Approach an extra attack at level 5.
I haven't had the opportunity to actually play a Troll Singer with the 5e ruleset. But it looks like you want to be more sparse with the use of your leveled spells compared to the other traditions. This I don't have a problem with, if it weren't for the apparent fact that they are just as "bad" as the other casters at martial fighting.
I think giving them an extra attack at level 5 (and no more extra attacks after that), would align them more with what the lore that says: "...most skalds are true warrior poets that lead their allies to victory using the great power of their voice and muscles."
Another option would be to give them the extra attack at level 6, just like how the Wizard: Bladesinger works from Standard D&D 5e.
This could of course require some rebalancing of other parts of their kit.
Would it make the Troll Singer too powerful if you gave the Approach an extra attack at level 5?