IMO vou are right about using three spheres. But don't use tactics, it has absolutely ZERO synergies with the secrecy concept . The tactics sphere is for fighting enemies, secrecy is for avoiding fights.
You should probably tell us which expansions you own. If you already have the first Hobbit expansion you should have a look at Nori. He only has a threat of 9 and will reuce your threat with each dwarf you play. I'd combine him with Théodred to get enough resources plus access to leadership secrecy cards. You can either play with those two (depends on the escenario) or you add Glorfindel or Bifur. That gives you a starting threat of 23/25, but with Nori, Arwen and some Elround's Counsels you should be able to get it under 20 quickly.
If you take Glorfindel he can be your fighter until you get Light of Valinor. Two spirit heroes allow you to play Ziggy and Bofur quickly. Then you can play Northern Tracker, Arwen, GG and so on.
If you take Bifur you can use him as a quester. That way he can gather resources up to three resources each round so you can play all those costy lore cards if you want to.
i respectfully disagree about the part about tactics not synergizing with secrecy at least in part. while secrecy is hard to do and if u include tactics it is harder still but at least in theory some cards like unseen strike, hands upon the bow, and quick strike allow legolas to choose his fights and then have enough strength to pick off all but the meanest of enemies. furthermore, legolas helps fill any questing wholes that there may be. other simple combos for this concept is if u have a dwarf in the deck or even have a tactics dwarven hero like gimli u can use khazad khazad and other major dwarven pound cards to simply beat the snot out of enemies when sneaking isnt enough.
truthfully, i dont play secrecy much as i havent found that it was worth the effort. keeping threat low is great but the secrecy cards arent enough to build around as yet in my eyes but dont disregard tactics completely.
I see. Of course one can cross the Alps with a bicycle instead of a car if he wants to.
All the cards mentioned, except of Unseen Strike (and even that could be discussed), have nothing to do with the secrecy mode. They're just cool cards.
Ok, you say you haven't played secrecy decks much which explains your PoV about Legolas. Yes, he can fill any quest hole, but one task of a secrecy deck is to avoid loosing quests at all cost. That's why you need at least 4 WP for your first turn, because otherwise your threat will possibly rise (which is no synergy with the secrecy concept at all). So if you keep Legolas as a possible attacker you also need to keep another character as a possible defender. And that won't work until you have enough allies in play. The concept of secrecy is to sneak around your opponents and only to engage them when you want to. There are of course scenarios that make this almost impossible, but these should be probably played with only two heroes to start with a threat below 15. Or they shouldn't be played at all with a secrecy deck.
And here we have the perhaps biggest disadvantage of tactics: It hase no heroes with a low starting threat. If you want to use Legolas, you have exactly 11 threat points left until you reach a starting threat of 20. And tactics has no threat reuducing cards or abilities either. And only few allies with some WP.