The past few weeks I was “fortunate” enough to pull a lot of 5* from different portals. Too bad that except for Lewena, they were dupes 
So, only in the last few weeks, I got:
New heroes:dupes - 1:6
What was your most significant dupe-pulling streak?
I got Fogg in back to back 10 pulls. GREAT hero, doubt I’ll need two but I’ll keep just in case.
I pulled two Vanda in two consecutive years. Fortunately, the second one came with a useful costume. Otherwise, my favorite all time hero seems to be Quintus. I can train, re-train him, pull him with gems or tokens with my eyes closed and one hand behind my back. I most likely got about 10 of them durig my E&P career.
Early in the game, once got two Panthers in the same 10x.
I have absolutely no idea how it happened or who I was wanting but I now have 5 morel
Maybe there is a morel to this story.
Yeah!
Save your gems
My dupe 5* drop rate has trended between a whopping 40% to 50% for as long as I’ve been tracking, possibly longer. That means, for every ten non-S1, non-HOTM 5* I pull, four to five of them are dupes… 
& My drop-rates definitely don’t trend close enough to (or above) averages to compensate this fact 
Lol the odds are against this many dupes with this many missing heroes per portal, yet, here we are
Although, lately, the dupes I’ve been pulling - aside from S1/HOTM since they’re a given - have been related to costumes. As in, I previously owned the original hero, however, the costume itself was new. So while it’s better than pulling a full-on dupe, it’s not quite as exciting as getting, say, a brand, spanking new hero. A few recent examples:
Literally the only silver lining to non-S1 costumes. Or else, pulling these heroes for the zillionth time would just be another reason to feel annoyed
I’d have to narrow it down to one portal - the Costume Chamber.
C-Quintus
2x C-Sartana
2x C-Joon
I’ve gotten an additional 2x C-Sartana from HA10 too (and no other costumes from HA10). 
I guess I’m pretty lucky when it comes to pulling dupes, I’ve never pulled a dupe S2/S3/S4/Event hero as of yet. But I’ve pulled 2x costume Isarnia and costume Justice. Also HA10 has given me 2x Ares and a dupe Miki.
Not sure if HotMs count for this, but these I’ve pulled quite many dupes. From oldest to newest: 2x Noor, 2x Zulag, 2x Glenda, 3x Bertila, 2x Frosth, 2x Devana, 2x Alexandrine, 4x Hanitra, 2x Iris, 3x Zagrog.
So I guess the 4x Hanitra was my highest streak.
On the bright side, you got the good one. 
So far only Horghall and HotMs. Two Iris, two Silvaria. Guess I’m starting my stockpile of trade ins with those.
I have seven. Seven Elena´s. Three of them gotten within the last two months, from event and Springvale.
So. Frustrating. 
Last Underwild did 30 pulls with coins got 2nd and 3rd Fogg. This Vallhala did first 12pulls with coins - got 2nd Bera. Half hour before it ended l bought 2nd day offers, did 15 pulls with coins and got - 3rd Bera
This is the part of soul exchange that is frustrating. Those are all A+ heroes, but three of them isn’t needed. Plus you get the same credit in the Soul Exchange as you would for an Obekan. Maddening!