I have to agree with Exu here. Biweekly is designed as an opportunity for people to develop their skills and knowledge by playing with monsters they don’t own in some reasonably challenging PvE battles. I mean no disrespect, but I do them all first try except for every 2-3 months a single challenge will require a couple of extra attempts. I believe everyone can reach that point once they have played the game long enough.
One recommendation I’d make is to play each of the two battles in a column before going to the next column. They’re the same enemies, so it nicely prepares you for the second battle because you know what to expect.
Yes it’s fixed now. Monster bonus for the player team is retained. I don’t think it retains if they’ve tweaked the entrance speed of monsters, but that very rarely matters.
One of the things I really hate about this league system is how stronger players get a much smoother ride than weaker players. It takes 90+ wins to get grand champion, but you can see in the grand champion thread that some people have to go to 200+ wins (I think a few even 300+) to achieve it. I’ve ranked down only once or twice and it felt horrible. I can only imagine how demoralising it must feel to continuously bounce around the leagues.
One of the problems is that the top players have insanely high win rates. Presumably there’s a pretty big chunk of players from the top who continually beat everyone else and make it harder for them to progress. The Devs have noted this many times and said how they’re trying to decrease this, e.g. by creating more of a rock-paper-scissors environment.
The Devs also made matchmaking be losers against losers and winners against winners (from the latest match result). This should, in theory, help stop too much ranking down in the leagues. I know it’s the main reason I almost never rank down, because my likelihood of two losses in a row is very low and three losses almost never happens. I think this is honestly the best thing the Devs have got in place for helping people progress through the league system.
That all considered, people have to make their own assessment of whether it’s worth it to try and go for grand champion. If you continually get ranked down, you probably don’t have a high enough win rate to do it. Not everyone will achieve it. It’s the same thing in PvE events where you don’t get all the rewards unless you can do the harder battles.
Presumably it’s regional pricing changes. That particular price bracket was much more efficient than the other shop offers, so maybe it was on the lower end of what it should’ve been and it’s now been bumped up.
For me it went from £11.49 → £14.99 which is also a 30% increase.
I was only ever buying the offers at that price (stellar ticket), so it’s probably priced me out of spending again 
once I had much worse luck on that event.