The accents on the downbeats of the cello are a little extreme. I'd try to pull those back slightly.
The hand percussion should be further back in the mix. While they tend to cut through in a mix, they would never be this present in a live ensemble since the room would have to be pretty big to accomodate such a big ensemble. I'd pull them down in volume as well as pull the dry signal back a bit so it sounds like they're further back in the room.
Violin performance is pretty good. I'd try to shape the phrases a bit more with expression to create a more believable performance.
The harpsichord is a bit too loud in the mix. Harpsichords are very quiet instruments, and in an ensemble like this, it would be further back in the mix.
1:22 - the transition here is a little abrupt. I think you could have tapered the instruments a bit more into the thunder sample.
1:59 - I would have liked to hear basses doubling the cello down an octave here to really open up the arrangement. You do a good job of building into this section, but I think it could be more. Perhaps switching to bowed strings in the background strings would be nice?
2:12 - this part stands out as a new idea that doesn't ever go anywhere. The previous section ends a little too abruptly, then this comes from nowhere. The abrupt ending of the previous section could work, but you absolutely need to develop this further to make it work. It's a brand new idea in the piece which is typically not something to bring in at the very end unless it's written for a movie and there's something on screen (in the case of a score) that makes the tag make sense, or perhaps it's a callback to an earlier section (or foreshadowing to a future one) in the context of a bigger programmatic piece (this happens in famously in Symphony Fantastique in quite a few places, but it makes sense in context). As is, I can only judge the piece by what is presented.
In general the production needs a little mixing love in post. The balance between the instruments is a little funny, and they all sound like they're from different sample libraries (mostly because I assume they are). This is typical of MIDI scores, but there are tricks to making everything sound cohesive. Samples for MIDI instruments are often recorded under the most idea/pristine conditions. While this offers a lot of flexibility in mixing and they sound great by themselves out of the box, they typically don't sound right when mixed with other instruments. This is partially because this type of music would be recorded as an ensemble in a large room instead of individual instruments in a booth. First, I'd do some work with reference recordings to get basic mix levels. Find live recordings of a similar ensemble and put it in your project, then bus all your instruments to a separate track. A/B between the two of them, and try to get yours to sound as close to the reference as possible. You'll learn a TON of tricks this way when it comes to manipulating reverb/eq/mix levels. Look at maps of how a traditional orchestra is laid out and realize that, while sections are spot miked in recording sessions, most of the mixing work is done to replicate the sound we're used to hearing in a concert hall (eg, percussion sounds further away because since it's the loudest and cuts through the air fairly easily, it's placed in the back of the room so it doesn't overpower quieter instruments like violins or harpsichord). When we work with virtual instruments, it's easy to forget what a live recording sounds like, but when you A/B it, it can help you make better mix decisions. If you want to get REALLY down with how each of your instruments work, actually transcribe a chunk of that recording note for note into the instruments, and then do the same A/B work. One of the tricks is to put reverb on each group of instruments to get them placed in the "room" at the right place and depth. Then, on the master mix, put a SUPER subtle super short reverb on everyting over the top of that. This will act as a sort of glue and pull all the instruments together into the same space. The main work will be done by the individual reverbs, but the final one will help smooth over differences between the sounds of the instruments.
All in all, nice work compositionally. This has a very Danny Elfman feel to it. A little more work on the orchestration and mix and I think this track will shine even brighter!