To that, I'd add:
Making the tension "who dies first" is not going to work very well.
Hypothetically, if they have 2 defenders and 2 leaders, the leaders and the defenders will work together very very well to keep PC's from dying.
So, I'd aim for alternate tension methods building methods, such as:
1. Battles with time limits. "If you can't accomplish X by the end of Round 4, bad things happen." .. This can be anything form "the evil wizard completes his ritual" to "the bad guy reinforcements arrive" to "the NPC-in-trouble dies" to "the good guy defenses start to collapse".
2. Battles with different goals. Starting from point A, get around/past defenders to reach point B. (The "defenders" for this one should be tougher than its worth fighting, or 'seemingly infinite in number'.)
3. Protect non-combatant(s). Similar to #1; there are non-combatants on the field of battle who are in trouble. The party has to spend some number of actions to keep them out of trouble. E.g., somewhere in the village of Blah is an old man who can tell you guys the location of the McGuffin. When the party reaches Blah, they find it being overrun, with bad guys visibly killing villagers in the streets. The object: protect the villagers and escort them (especially the old man) out of the village to safety.
4. Split the party. No, seriously - not permanently, just for some fights. You can use a portcullis, a pit trap, a slide, any number of things. Drop half of the party into a battle tough enough for the entire party ... and leave the other half trying to figure out how to get there from here.
4.a. Alternately, the portcullis drops, and it turns out the melee attackers are coming from behind, where they're now threatening the ranged strikers, controllers, etc.
4.b. You can achieve much the same thing with creatures that arrive at the edge of the map at the start of Round 2, and roll their own initiative.
5. Use enemy controllers liberally. Focus on walls, zones, etc: things that divide the party. This is essentially the same idea as in number 4: anywhere you can create local superiority for your creatures will create some significant tension for your players.
6. Use enemy soldiers sparingly. (They can last too long - though any BBEG you're counting on lasting for more than 2 rounds will need to be a Solo soldier.)
7. Use morale for bad guys - when you're writing an encounter, write the "script" of "when certain bad guys will break and run". For example, the goblin archers might break and run when the last of the wolves goes down, or dropping the BBEG might cause any of his surviving hirelings to flee/surrender, etc. Likewise, that BBEG with 1200 HP might be willing to offer some Diplomacy when he's down 500 HP and all of his minions.
8. Offer "mop up" to the players. For example, "If two players pay one healing surge, I'll let you guys mop up the rest of this lot 'off-camera' so we can move the story along.."
(7 and 8 are almost necessary for limiting "grind")
9. Use negative environmental effects which hurt the party's action economy. For example, a swinging rope bridge that is tough to move across safely. A battle on the deck of a ship during a raging storm, where some PC's will need to be spending Standard actions on keeping the ship from sinking, etc. Archers firing down from a second story balcony, with the Jump and Climb rules slowing down any melee fighter who wants to get up there with them, and the balcony railing providing Cover against ranged attacks.
10. Use lethal environmental effects which threaten insta-death but offer a "if one of your friends bails you out" moment. For example, that ship in a storm, perhaps there's a chance of a huge wave knocking people overboard ... then its "Standard action as an Endurance check to keep your head above water for another round; it'll take help from your friends to get you back shipboard before you drown." ... or if its an airship battle, allow "falling" to happen at the start of any airborne character's turn (cartoon-like) rather than as soon as they are airborne. That'll give you "rescue him before he falls" moments, like Nightcrawler's rescue of Rogue in X2.
.. Okay, so none of these are 100% specific to big parties, but hopefully they do give you some inspiration about how to keep encounters interesting even though the 9-PC-party would walk through most stand-up, knock-down fights easily!