this attribute on the item ONLY APPLIES TO THE MERC, and why infinity rolls don’t matter.
Some questions:
- Why are you using such a weak skill as wake of fire on a trapsin? Fire blast is MUCH stronger, even stronger with infinity and enough trap skillers. Fire blast is also synergized by light traps.
- Did you max all 3 light traps? Because if you did, your damage should be very solid. In p7, you use 5 x LS instead of DS but infinity increases fire damage of corpse explosion, the immunes who are left can be killed with death sentry+fire blast. Light immunes are some of the most low HP monsters compared to fire or cold immunes.
Not enough skills, too noob
ad 1. As it turned out Wake of Fire looks weak only due to listed in tooltip damage, in fact it seems to deal way more damage; the only weak part of the skill is number of shots, just 5 opposite to 10 other traps have. I’m using it as AoE fire damage source as these missiles cover quite large area, ofc I’m throwing Fire Blasts too once set traps. I’m using Wake of Inferno against single targets.
ad 2. Yes, I have maxed Wake of Fire, Fireblast, Lightning Sentry, 1 point in Death Sentry, and 4 in Wake of Inferno. I also maxed Charged Bolt Sentry as synergy, and have few(around 5) points in Shock Web, with time I’ll max that one too.
And my damage is so solid I haven’t noticed much difference with or without Infinity till I faced monsters with higher HP, like Urdars, so for my current situation mana regen from Insight > damage boost from Infinity.
Although yesterday I’ve finished Act III, things may change in Act IV.
Your light damage isn’t maxed then if shock web isn’t maxed. My priority is different to yours when playing a trapsin. I max all 3 light traps before moving to fire blast to have something against immunes in hell. Not enough points for anything else until that point. And yeah, infinity primarly increases light trap damage. If it isn’t maxed no wonder you barely feel a difference in clear speed.
We cleared that up then.
To be fair I don’t play ladder. Never saw the point. I mean I don’t trade so why bother. 
There is a lot to learn about the game through trading you have to at least use discord though. There are things so rare that you will never find them yourself.
Can’t say I honestly agree with that. Maybe if you play ladder and are limited to a time frame. There are VERY few things I haven’t found over the years, and TBH none of any of those were something I’d use either way. I mean at that point you are just talking about very specific jewelers mod perfect rolls… and frankly I just don’t care about those lol.
I’d much rather use an Enigma, Fort, Phoenix, Spirit, Exile over a j-mod chest/shield with facets/jewels personally. I don’t care about PvP, or organized split farming, and I don’t play offline so the conveniences of those items outweight the slightly higher damage.
I mean I’ve found every single unique, rune, charm combo, jewel, things like +6/40 javs ect before. So other than a couple specific perfect j-mods and a full inventory of perfect 91+ charms can’t say there is anything I’d ever needed to have traded for. And “needed” is a very misleading term to begin with. I mean the only reason I play D2 is to farm for rare items to begin with.
I mean heck the only unique/rune I haven’t found on NL so far on D2R is T’s Might, Mang Song (neither of which I care about) and a Zod. Already have 4 arachnids, 3 griffs, a CoA, and have found 2 ber, 2 jah, 2 chams 
.
Makes me wish javelins had 4 sockets. Could you imagine that AND insight on merc.