Don't worry about Shana getting her DS, the pacing of the game is one of it's strong points. At the beginning of Disc 2 and Disc 3, the story stagnates a little and the game forces you to spend time in a city(different cities between discs), but they have their own reason and purpose, so I really don't think it detracts from the game.
As someone mentioned, one of the flaws the combat has is that, the farther you progress, the less useful Dragoon Additions become, if you play with a physical team, then your regular human additions will own the Dragoon form.
However, Shana and another character that you haven't met will be incredibly powerful with magic, and Dragoon Magic, so if you want to use them with Dragoon forms are really powerful and useful.
But, Shana doesn't really need the Dragoon form, personally, Lavitz was one of my favorite characters in the game, he's strong, has high HP, and is not as slow as the other bruiser you will meet. But Shana and the other mage rely on magic to function correctly. Use the magic attack items you encounter, like Burn Out and the like, with Shana and you will see the power a magic character wields.
Another tip, notice that when you use the "Guard" option, you will regain 10% of your total HP. Reserve healing items for boss battles, if you are low on HP, chances are you will find something that will replenish your HP when you reach a milestone on the area you are traversing(like Pireflyes, clean water, etc.), or you could find an encounter with weak enemies and exploit them. Notice how every map has one type of little minion monster, weak hp, weak damage. Kill the rest of the enemies on the opposite side and leave only one of this pests alive, Guard away until you have full HP and then move on.
Additions are faaaaar more important than levels, don't grind for experience, it's hard to level up with the grunts, bosses will give you the levels you'll need. Instead, farm for addition levels, if you are close to a milestone that replenishes your HP, and you are close to reach another tier in your current addition, spend some time leveling that up. Final additions can only be obtained after you master all your previous additions for that character, so don't start using Volcano without mastering Double Slash, because you won't get the final addition until you do so. You don't need 99 uses, only that the addition reaches level 5, I think 80 uses is enough.
All party combinations can defeat the game once you know what you are doing, but keep in mind that because this is turn based, Speed is the only stat that truly matters, because more turns yield better results than big damage or incredible resilience.
This game plays more like a WRPG than an JRPG, in the sense that there's never really a need to stay in one place and grind endlessly, so just go ahead and keep progressing the story if you wish, most side-quests are open for the entire game(at least the ones that count).
Keep you eyes peeled for that Stardust, the only side-quest that matters depends on getting all the pieces. Check every corner if you want to face the special boss in the game, if you don't care or are planning on doing a second, more thorough, run later, then just enjoy the ride and don't bother.
Try to keep at least 6 Angel's Whisper if you feel the enemies are steamrolling you, this way everyone in your party can be revived twice. If you are the one with the upper hand, then keep only 3, so if the stronger enemies later in the game deliver those pesky instant death attacks, you are covered.
Try to keep 3 physical ailment restores(forgot the name) and 3 mental ones. Turning Dragoon will cure any status ailments, but sometimes you may wish to save your Dragoon levels for the Boss, and one ailment prevents you from earning more SP, so it's better play safe and have 3 of each. Again, if you feel you are steamrolling the enemies or prefer to use your human form(like myself), then perhaps 2/2 is better or even 1 physical and 2 mental.
The rest of your item limit fill it however you see fit, I prefer MP regenerating items like the Serenades, or Healing items if you use a party of 3 warriors.
Or if you want to use the mages, then save the powerful all enemy attack items.
Play against your enemies weaknesses, all enemies have a color on their name, that's their innate element. Counter your enemy with their opposite element to deliver massive damage. Light - Darkness, Fire - Water, Earth - Wind. Note that Dark Blue is Darkness, Purple is Thunder, Thunder is the odd element out and thus has no opposite.
Well... I am sorry if most of this things you already knew or figured out by yourself, but I wanted to give you a few tips so you can enjoy the game and don't be put off by finding yourself in a bind. Actually... now I want to replay LoD again =P
Maybe I will...
And you should play Plants VS. Zombies, it's fun, addictive, and has this "arcade game" feel to it that is just charming. At least give it a try, if you don't like it at least you can say you know the game.
