The following text is what I posted on the Steam website, which summarizes my personal take on solo play in BG3 (Tactician is implicitly assumed, otherwise solo play would be quite meaningless). Hope it may be of some help to you. By reading newer posts, I guess your solo char wasn't unexpected: Darkness coupled with Devils Sight, high mental abilities coupled with naturally low STR, etc. Honestly, in the end I still don't know how your emphasis on "jack of all trades" is related to the damage output you discussed at great length. But I hope you have found what you were looking for.

== below is what I posted on Steam ==

1) As for the gameplay, I think the hardest part of solo BG3 is not how the character performs in the end game context with a lot of fancy gear already filled up in the stash. But this question: How to get to Baldur's Gate, with or without dying at least once on this journey?

2) As for the build of the char, the most important question is: how often to respec? If respec is involved, the actual solo character is no longer a single build, but a combination of two or more builds, which may require potentially very different or even conflicting playstyles/gear/etc.

3) As for the roleplay part, the most relevant question is: Will any major/significant quests have to be skipped or only to be completed as unfinished? (Note: quests can be "completed" if the game thinks it's no longer possible to complete them.) Surely, most companion quests are gone or can only be completed in a more or less superficial way. Any other quests to skip or to be left behind? Also, do you plan to skip a large portion of the game by intentionally making use of a certain dead companion?

Also, ideally, the following questions/concerns are addressed upfront while planning the character:

4) Unless permadeath is the rule, how often is it acceptable to reload? As nobody is supposed to join the player party for the entire playthrough (except when and where it's enforced by the game to be otherwise), whenever the player char reaches zero hit point and can't automatically be healed, it is game over. Either treat this as permanent death, or a reload is in order. How often is such a reload too often to be acceptable?

5) How often to use potions? Is using potions an intrinsic part of the underlying build?

6) How often to talk to NPC before (tough) battles? This is the most relevant question when it comes to metagaming. If a player knows a tough battle will break out after triggering a talk, they may skip the talk and try to surprise potential enemies by simply attacking or ambushing them. A solo assassin build may require that the player skip as many pre-combat talks as possible, in order to make full use of subclass benefits. I personally hate doing this, even if it means I'll be fully surrounded/surprised once the talk is over.

7) Finally, the ultimate question for solo play in BG3 is: How to deal with the 75% loss of power by going solo vs party?

In BG2, I enjoyed solo play as much as party play - that was on Insane difficulty. Solo play is much simpler than managing a full party, yet a solo char can be built in a way to make the loss of party support eventually irrelevant in combat. In fact, a solo char can be built to be so self-sufficient in combat, that after Chapter 6 of BG2, a single char can keep a full party alive without the other 5 idling party members helping with any battle (well, other than doing something to help keep themselves alive if the whole party is ambushed or otherwise under attack).

In BG3, all 4 party members are technically equally powerful. Unlike in BG2, solo play in BG3 means the player loses 75% of combat power on a permanent basis, no way to make up for such an extensive loss of power. If solo is considered easy, then a full party play will be considered 4 times easier.

8) For BG3, I haven't figured out any build to be fully capable of solo play. I think the only real question worth asking in the end is: How to counter the underlying combat mechanism of this game after losing up to 75% of power in combat by choosing to go solo?

I personally believe, what is needed for solo play in BG3 is not a single build or a self-sufficient char, but one or more ways to counter the game's combat mechanism and a char who can do that.

One way is by using/abusing Darkness. Over 99% of NPC in this game can't handle magical darkness properly. As a result, a level 2 Warlock under a player's control can hide in magical darkness and attack to kill just about everyone within range without worrying about immediate retaliation.

Another way is by using Invisibility (spell/potion, not skill/ability). Unless you have joined combat, if you walk around invisible, most NPC will completely ignore you. You are free to go anywhere, discovering new places. You may even speed up or break a quest this way. All that, until you lose invisibility. Being magically invisible enables the player to possibly skip tough battles (at the cost of losing XP), or if that's impossible, at least make tough battles to most likely start in a way favoring the player.

Yet another way is by relying on potions to raise STR to a super high level and then playing as a Tavern Brawler for a full day every day. This enables the player to do massive damage both in melee and from a relatively safe distance.

== end of post ==

hope it may be of some help to some fellow players.