Yikes - that is a bit of a gap!
The main thing would be Saved Covers, no more race to champ covers on the vine.
The new/current Meta’s are:
5* Thor & Okoye - Thor runs at half health for constant AP generation in red, green and yellow, Okoye is a true healer who tanks for him and has a power in black with increase damage on powers. Okoye works with many other combinations of characters also due to her black - referred to as Thorkoye
3*/5* Thanos - he is used for clearing fast low level PvE nodes thabks to his passive Black AOE that triggers when an enemy is downed - use him with healers or meatshields though as a percentage of damage is also caused to his tema mates (but not him)
3* Dr Strange - he has a counter attack passive that triggers whenever an enemy fires a power, including goon countdown tiles so he wrecks at PvE for those nodes if you don’t have meta. There is a 5* version also but obviously he is buried in classics hell.
Gritty - This comprises 5* Kitty Pryde and 4* Rocket & Groot. R4G at the BEGINNING of their turn put down some hefty strike tiles. Kitty then uses her yellow passive power to buff these strikes tiles (and other specials) as long as there are a certain amount on the board. This results in absolutely insane levels of match and/or passive attack tile damage in a very short term. R4G is a part of many other meta teams also, he is frequently paired with 4* Gamora as having another Guardian on his team boosts his strike tiles even more and she has useful powers like a cheap stun.
Bishop - Bishop is often played with the above Gritty team. He has a passive that moves him to front once your team has absorbed a certain amount of damage and then retaliates once he has received damage past a further threshold, However what makes him such a nightmare is that he generates vast amounts of blue every time this happens which enables him (or another character on your team) to stun the enemy - you can quickly stun lock an opponent in submission.
Sabretooth - Sabretooth is a recently released 4* but he has use for 2 main purposes - first he has a passive power that when he matches an enemy strike tile it causes a 3 x 3 board destruction - this can be used to dismantle Gritty teams by taking out the specials they need to wreck. His black active also can create 1 point strike tiles for the enemy which he can then match for the above effect. His red is very cheap and if teamed with Okoye can cause havok - 4* Valkyrie has a similar power but Sabretooth is just much cheaper.
Medusa - Medusa team heals when you match specials and generates AP when you match enemy specials. Lots of teams but frequently paired with Carnage thanks to his special tile passive - referred to as Cardusa
You also completely missed the fearsome reign of Gambit! Both 3* and 5* versions had to be nerfed and were nerfed into oblivion.