Shield should be the top priority. It saves your teammates asses. In all Honestly, Spikes is the last set of skills i upgrade when i'm after level 15. I don't do mulch, and I use a primarely support build. The only question i have for myself is I usually go allthe way in compost, but I honestly have no idea how much of an effect it has on my minions. (I don't do uproot, i feel as if its a waste).
My 2 cents. I just don't play QoT aggressively. I make sure my teammates are able to run down targets with a strong sheild.
Don't get me wrong. Shield is good. Shield is GREAT even. However, I think it's a common misconception of many players that max shield = longer chase, therefore greater chance of kill. Think of it this way. When you give the ally a shield, you are letting them chase for longer. Enemy demigods have a movement speed. Speed = Distance/Time. The more time your opponent spends running, the more chance they have to get back to their tower, or escape. On the other hand, spikes lowers enemy armour, which means they take more damage. With increased damage, the enemy has less time to run, which means at the same movement speed as an enemy running from a shielded enemy, the distance they run will be less, meaning your ally not only is less likely to have to run through enemy towers or creep waves, but are likely to end the kill faster, which means they are able to get to other locations on the map quicker, and therefore support the rest of the team more readily. Given that the shield only really becomes useful when there are other enemies trying to attack your ally as he runs, you should use the "chase time" to go into closed mode (it doesnt stop you moving) and get ready to support the hunt. By having shield as second priority, yes, it's going to be a lower level, but all you REALLY want to buy your ally with shield is reaction time. so even though the damage absorbed is less, you're doing yoru job by giving them the time they need to abort the chase if situations really get bad. Honestly, the few hundred extra absorb you get between two levels will help you get kills less often than the extra drop of armour given by spikes.
I know a lot of people use closed form almost exclusively, because it's safe, you have higher armour and easier access to your defensive spells. However, what you're really doing to yourself is denying yourself the ability to really hurt the other team, and give your allies the support they sorely need. If you go purely defensive, sure you help your allies kill, but if they have 3 offensive characters, and you have 2 and a defensive queen, your allies will be hard pressed to hold ground, and therefore get the all important warscore. The offensive build for QoT I suggested before not only has more ability to drop enemy creep waves and demigods, but also doesnt really sacrifice any of her defensive capabilities in the long term. You still max your shield (for Godess of Thorns, which is an amazing ability) and spend skill points on toughening up your minions, but you also get a lot more offensive power. Remember, the extra damage that your minions get from the spikes lowering armour is higher than what you're going to get from spending the points of spike on upgrading minion damage through compost, or just straight stats.
QoT IS a support character, but you can't think of a support character as a "Defender". Yes, she has trouble killing on her own, because her burst damage isn't nearly enough to catch opponents off guard, but using spikes she increases the burst damage of your allies. Allowing them to catch even the best of players off guard. It's at this point, when you are pressing the advantage, where you use shield to buy extra time for allies chasing (assuming you arent fast enough to help chase yourself, because remember, when you cast shield, you DO stop for a split second, and if you're the same speed as the person you're chasing, you no longer are dealing damage if you're just in range, In this case using shield is hurting more than helping) If you're faster than the opponent you're chasing, just get up close for another spike wave. Shield is also an escape. You buy your allies, (or yourself) reaction time. I like to stay near middle where possible as queen, and I always buy Teleportation scrolls, so when my allies are running on low hitpoints, i can teleport to the tower nearest to them, shield them, and then turn offensive and spike thier chasers, then really making them questino whether or not it's worth it to try and keep chasing. after spikes go back into defensive and get ready to shield yourself in the case thatt hey turn on you, or your ally in the case they ignore you.
Once you know WHEN to use your abilities, then you know when to be open or close. To just simply dismiss open form as an option due to teh weakness of the other abilities like uproot, and the loss of bonuses, you're dismissing the chance to improve yoru skills with queen, and use her full potential.
Queen is one of the harder heroes to play well, but once you start getting the hang of her, she's easily one of the most powerful, especially in team games.
