CORRECTION: The Corpse Lance Affix is now only giving +3.3% Movespeed, instead of +10%. It appears that after this recent update, the +Movespeed buff from Corpse Lance Affix is now being strifed in BGs.
I have been using the same exact build for Battlegrounds for the past 2 months. Having 4/4 of the Corpse Lance Special Class Magic Affix (Aka Eternal Affix) that gives a stacking +10% movespeed buff for 3 seconds, ontop of +20% base movespeed, it brought movespeed up to +60% in Battlegrounds as well as anywhere else in the game. And its been that way since the Special Class Magic Affixes were added.
While doing Battlegrounds last night, I used my Wiltbloom Golem Suit build and it feels very fast. My Corpse Lance build is even faster normally, however once I switched to it I felt drastically slower than normal. And it was no different in or out of combat, everything just felt slow.
I had just used these same builds last week, and have video of them showing that it was giving the full +60% movespeed while in Battlegrounds, and outside anywhere else. After a couple matches I went and checked my stats during a Battleground match, and noticed my movespeed was only +33.5% after using Corpse Lance with 4/4 affixes. That was from +20% base movespeed, and my Bottled Hope giving +13.5% movespeed. When Bottled Hope was on cooldown, I noticed my movespeed didnt seam to change AT ALL.
I then took off Bottled Hope and just had +20% base movespeed and the 4/4 Corpse Lance Affixes. Outside of Battlegrounds, it gave +60% movespeed like it always has. However, in Battlegrounds it only game +33.3% movespeed after casting Corpse Lance with 4/4 Affixes and +20% base movespeed.
I tried 1/4 Corpse Lance Affixes with +20% base movespeed, and got +30% movespeed outside of Battlegrounds, but only +23.3% movespeed inside Battlegrounds. With 2/4 Affixes gave +40% movespeed outside, but only +26.6% movespeed inside Battlegrounds. 3/4 gave +50% outside, but only +30% inside Battlegrounds. And again 4/4 Affixes ontop of +20% base movespeed gave +60% movespeed outside, but only +33.3% movespeed inside Battlegrounds.
All other Special Class Magic Affixes seem to be working as they normally have, except the Corpse Lance Affix for sure. There might be others with issues, but I’ve confirmed in both Battleground test and in live matches, it is giving only +3.3% movespeed per stack!
Edit 1:
I have gone and tested the Command Golem Affix and confirmed it is NOT working at all in Battlegrounds either! In a real Battlegrounds match it does not work at all.
However, I have been able to get it to work in Battleground TRAINING.
Entering the training match, with 4/4 Command Golem Affixes and using Wiltbloom Golem Suit, at the start of the match I can see that the 3rd Ability Soul Blast has default range, the same as if it had 0/4 Command Golem Affixes. But if Ichange Legendary Gear for one of the slots that has a Command Golem Affix to a piece of gear that does NOT have it, going from 4/4 Affixes to 3/4 Affixes, the +30% Size and Range buff from the Affixes now works! And if I then re-equip the gear with the Affix to go from 3/4 Affixes back to 4/4 Affixes, the Size and Range now receives the full +40% buff! It went from no buff at all with 4/4, change to 3/4 to get buff to work +30%, and change back to 4/4 Affixes for the +40% buff.
Obviously, theres no way to change gear in a real Battlegrounds match, so currently there is NO WAY TO GET THEM TO WORK IN BATTLEGROUNDS.