I agree.  The new Garritan Orchestral String (GOS) tutti KS sections are a bit odd on their own. For me, the GOS Tutti String sections can be interesting 'as is' if layered up with some other string stuff, but  on their own....they require some major tweaking.

I do like the new GOS solo strings to some degree (depends on the context it's used in), and the small group sections are actually quite nice and easy to use.  The new GOS solo strings require judicial use of CC119, CC68, and the right mix of key-switches, but they can be nice if you need a louder and more powerful soloist. 

I pretty much keep CC119 set to 127, and use the legato pedal frequently with the new GOS solo strings.  I'll use lower CC119 values if I want a bit more up/down bow at the beginning of a theme or passage.  During rally fast passages, the shorter bow articulations, and the detache key-switches are also quite helpful.  So, it's possible to get rid of a good 90% of that funky 'bow swell' effect with the solo strings.  If the tempo is fast enough, clean runs are quite possible as well by hopping over to detache, martele, sautille, etc.  Do ignore what the articulations are named in the library, and use your ears to simply pick and choose what happens to work best for a passage :)

Someday I'm going to attempt to have a key-switch that loops the detache samples (or some other choice portion of a sample) as well, so I can get a bit more flexibility on slower runs and passages where I don't want vibrato or amplitude swelling effects.  I guess it'd be something like a 'simple, no vibrato, scale' mode?

I don't think it is part of the official documentation, but while poking around in the SFZ I discovered that CC119 can be used to change the sample offset (where ARIA starts playing the sample) to some degree.  So, a higher CC119 value will start the sample later, and give the impression of a faster attack.  Also, using legato pedal CC68 can help cut out some of that long and slow attack.  CC68 creates a kind of overlap/crossfade between subsequent notes.

I have not really had time to dig into it, but it is possible to fix things we don't like about Garritan Libraries as users to a pretty large degree.

Examples: 

Some instruments need their range increased a little.  Some instruments have some bad loop points for some notes (Oboe D'Amour as one example).  Sometimes there is a bit of bow noise or something at the start of a sample (fine if occurring just once in a random place) that can get too repetitive and unnatural in an actual sequence (GOS Tutti martele for viola), so one could change the sample offset (starting point).  Sometimes the dynamic envelops are close, but not quite right (situational needs).  Some of the drum kits have round-robbin bugs (GM MIDI Drum Kit:  first hit works, second is silent).  Sometimes one might like to add new key-switches for more user-created articulations.  For orchestral percussion, sometimes we just need to go make our own sample of something real quick and somehow get it into ARIA as part of one of our percussion kits.  Etc.

As a user, one can edit all this stuff in the instrument's SFZ file (Do make a backup copy of the sfz first).  It is a text file containing simple opcodes.  The concepts are not all that different from tweaking virtual knobs and stuff in a virtual sampler/synth like Kontakt or Halion, but instead of using some fancy UI, it's all laid out in a text file, and it's based on simple tags (opcodes).

The included samples of Garritan Libraries are slightly encrypted (phasing and such is altered, and ARIA fixes it in real time); however, one can open them in the free Audacity DAW to get enough of a waveform overview to get an idea of things like loop-points.  It's also possible to 'resample' things if you really need to 'edit' the sample itself.

ARIA can also play regular WAV, AIF, MP3, OGG stuff as well.  So it's possible to bring in 'your own samples'.

One can find information on the opcodes here:  http://drealm.info/sfz/plj-sfz.xhtml

ARIA specific opcodes and support can be found here:  https://www.plogue.com/plgfrms/viewforum.php?f=14&sid=1b82025214aa8a119fe8b8473de97f0c

Here in the forum users sometimes share edited versions of SFZ files as well.  I've provided a few for extending the range of the choirs, and fixing some drum kit issues.  At some point a user provided an Oboe D'Amour loop point fix.  Etc.

In short....unless you use a tracking DAW (Very hard to use these new tutti strings with a scoring package like Finale/Sibelius/Dorico), and want to open the SFZ file and do some tweaking, just use the new GOS Tutti stuff only when layered up with something else.  I.E.  It can make a nice overlay for lush mixes if you have a slot using a legacy solo, or tutti violin 1 section, and another slot with the new GOS tutti set to the same channel, and have CC119 set to 127.  

Out of the box, even with the CC119 and CC68 tricks, the GOS Tutti strings are just too 'laggy' on their own, due to the long attack (It's as if the note starts with the bow from a dead stand still)....unless you're using a tracking daw and can just slide the MIDI note on events around easily....it's almost impossible to get them to sound 'in time' with the rest of the instruments.  Someday I'll take a closer look at reworking the SFZ files to take advantage of the samples....but till then, I simply don't use them all that much.

The good news is, all the String stuff from GPO4 is still there, and it all works and sounds and it always did.  One can ease into using, understanding, and correcting issues with the new GOS stuff.  It's great stuff to have for a tracking DAW user for layering up and getting more textures throughout a piece, but it's not likely to be the default slate of 'go to' string sounds for simple composition and play-back stages of a project.