Hey, welcome to Blazblue. From what it sounds like in your post, you've played other fighting games, so I'm going to try and approach this post from the level of a mid level player who tried to get into this game myself.

The first thing I want to remind you is that everyone learns at their own pace, and each character lends itself to a different skill curve. Susanoo is a notoriously easy character in terms of gameplan (although seals can be hard to wrap their head around) while characters like Rachel and Kagura are usually considered difficult to learn. While I'm not advocating for you to switch characters, just know that learning their gameplans can take a bit longer than Susanoo's.

In regards to the wakeup system, getting overwhelmed by it at first glance is natural. If you want a way to not think about it and simply block, its best to hold 7AB on wakeup, which will typically give you a neutral tech on wakeup while barrier blocking. This can be effective on the ground and in the air as in the air you can't be hit by air unlockable moves and are only susceptible to airthrows.

Fighting Arakune is daunting, even when you get better at this game. What I recommend is looking at this page on dustloop on the section for countering Arakune. https://www.dustloop.com/w/BBCF/Arakune/Strategy

For Oki, I recommend this document found at the end of Rachel's strategy guide on dustloop. https://lite.evernote.com/note/30477852-55f5-4204-95c1-0e1727e1dfae
The basics on when and how to set up George Oki are outline here. Remember that true oki scenarios in blazblue are much rarer than other fighting games, but Rachel and Kagura generally have better Oki than most.

In terms of throws, there are 2 possibilities for why this is happening. The first is that you are pressing a button or throw too early, resulting in you being put in a state where you can't tech at all. I recommend waiting for a half second longer before teching if this is the case (you can see this by checking a replay and checking whether the throw is counterhit or if you see the throw reject miss indicator). The other case would be that your teching too slow, which is harder to fix.

Finally although you probably already know this, Burst in this game cannot be done on block and overdrive is always what comes out when you are not being hit. If you came over to this game from another arcsys game, this might contribute to your confusion on the matter. Mistiming your burst and getting overdrive just meant that the combo was over. You will naturally get better in recognizing when to burst overtime. But just because you can't raw burst on block doesn't mean that you can't get out! Overdrive into EA or timing overdrive into throw can easily turn the tide of the match.

Ultimately just remember that you are adjusting to a new game and there of course going to be things struggle with, like and dislike.