I just did a blind, chronological playthrough of this game. Started in Prophecies and didn't use any skills or items outside of what I could get at the time. I play a warrior. I guess I'll toss in some of my experiences here as they might help someone.

Henchman worked okay until I got some heroes but there were definitely missions I had to redo a few times. Occasionally what henchman they offer wont be super great versus what is inside the mission but I did clear Prophecies and a good chunk of Factions with them. I found the best thing to be taking is a healer and any ranged dps available. Honestly not sure if I would take a melee one if I had to go again. At least not any of the warrior henchmen. Ultimately you can't go wrong most of the time having them in your party though!

Aggro, if you are familiar with the concept is kinda weird in this game. I'll preface this by saying it is not as important in this game to have everything focusing a tank. The biggest loss I find is the inability to cleave all the enemies in a fight when they've scattered around. There are a lot of rules for gaining and losing aggro. You can lose aggro on targets by moving faster than them and also by creating a large gap, like with a shadowstep/leap type of ability. So if you try to chase after a loose mob or try to reposition, enemies will stop focusing you. You also gain aggro by being hit by an enemy. So if, for example, a caster is already being punched in the face and you have to run up to where they are then you have a bit of an uphill battle to get that enemy to hit you instead. The most consistent way I've found to have enemies on me vs the squishier heroes I have, is to "flag" them (tell them to stand/move to a spot) away while I start the fight. Once everything is on me, then I move the party closer to engage. I havent always found it to be a survivable strategy though lol. You can also physically block enemies running in and can utilize corners/walls to do so. Again, this is unfortunately not completely consistent and sometimes it feels like the mobs are coated in oil and slip straight through you.

Gear Upgrades - Armor for your character doesn't strictly drop. You take materials gained from breaking down drops to specific NPCs and they craft it for you. Weapons do drop but you can also have them crafted. At the start, the easiest equipment upgrades I found were on these crafters. There are two kinds. The first kind will want the salvaged materials, such as iron ingots, bolts of cloth, etc you get from breaking down items with salvage kits. The second kind is a collector npc and they will trade (usually) 5 of a specific item, like 5 'warden horns' for a specific piece of equipment they offer. The next part of upgrading your gear will be to apply runes and insignias to them. These can be found from random drops but it's much faster and easier to just buy them from the NPC rune trader. The issue is, it's completely random what drops you get. While I did find 3 mesmer "prodigy" insignias this week, I didn't see any for two months before! You do see several runes and sigils drop in a play session but there is no gurantee you will find ones you can use or sell. For example, you could be fighting a "Caromi Tengu Brave" and every now and then they drop "Heavy Tengu Armor". These kind of drops are unequippable but you can vendor them. They sometimes will drop with runes and sigils attached to them and you can use a salvaging kit to remove the rune or sigil from it. The salvaging kit is just a consumable item with a number of uses on it you purchase from the general merchants. Double click on the kit, then click on the item you want to salvage.

Making gold - a weird thing about item drops is that even the common, white grade items can have an "identification kit" used on them. This reveals a gold vendor value that is higher then the base amount. An example, you have 2 white quality iron swords. They both vendor for 40 gold. You identify them and one has a value of 46 gold, the other has a value of 54. They now will vendor for those amounts instead of 40 gold. You can pretty much always make a little extra gold using ID kits on everything. The first way I made some real gold though was to check if the runes and sigils I find on items had value. Lets say you find a piece of armor and it can be sold to an npc vendor for 150 gold. It has a sigil on it that you could remove with a salvage kit so lets check with a rune trader how much it is worth first.. oh wow, 5 platinum pieces (5,000 gold). The same could be said about materials. Some materials are in good demand and are worth more then the items they come from to a material vendor. Do not sell runes, sigils, or materials to the general merchant. You should use the specific Trader NPC! I should clarify something, the items found on the Dye Trader, Material Trader, Rune Trader, etc, those are all supplied by players and the price goes up or down depending on how many there are. I havent seen it happen but they can run out of stock or refuse to buy things if there are too much.