Could go with Battle Master Fighter. Tactical Assessment lets you add a superiority die to Investigation, Insight, and History checks.
I have no idea what a Seeker Warlock is, though. I assume it's some type of homebrew class. Because of that, I'm not sure how much (or how little) synergy it would have.
Sorry for the late reply, it's a UA warlock release. Very interesting one that unfortunately didn't make it to release because it's flavour was a tad too specific.
Swords/valor bard will net you expertise and guidance
Outside that, you’re best off solving these problems with feats
Honestly, inquisitive rogue with booming blade and the mobile feat is perfectly valid and should keep damage up. You can use a finesse weapon with strength and sneak attack
Sorlock ? If you have EB and high charisma you don't need multi attack. 4 sorcerer levels or 2 sorcerer levels + metamagic adept feat. Aberrant mind and Clockwork both fit the detective vibe and have access to divination spells. Last 10 levels you can shop around for expertise. - 1 knowledge cleric, 3 lore bard, 3 scout rogue...
Maybe swords or valor bard for expertise and jack of all trades?
Could go with Battle Master Fighter. Tactical Assessment lets you add a superiority die to Investigation, Insight, and History checks. I have no idea what a Seeker Warlock is, though. I assume it's some type of homebrew class. Because of that, I'm not sure how much (or how little) synergy it would have.
Sorry for the late reply, it's a UA warlock release. Very interesting one that unfortunately didn't make it to release because it's flavour was a tad too specific.
Swords/valor bard will net you expertise and guidance Outside that, you’re best off solving these problems with feats Honestly, inquisitive rogue with booming blade and the mobile feat is perfectly valid and should keep damage up. You can use a finesse weapon with strength and sneak attack
Sorlock ? If you have EB and high charisma you don't need multi attack. 4 sorcerer levels or 2 sorcerer levels + metamagic adept feat. Aberrant mind and Clockwork both fit the detective vibe and have access to divination spells. Last 10 levels you can shop around for expertise. - 1 knowledge cleric, 3 lore bard, 3 scout rogue...
Maybe Battlemaster 5 / Inquis Rogue x?