Expanding @arotter's answer, my preferred method of marking at range is with half-elf, hand of radiance, and dabbling defender*. You can mark up to three targets that way, and you'll be able to keep it up every round (if you have nothing better to do) in paragon.
Beyond that, any ranged power and defending dabbler is an excellent choice for marking, as is soldier of the faith.
However, looking at the meat of your question, I have a different recommendation. Given that your objective is teleportation, I'd recommend multiclassing warlock and, next level, taking the warlock's at-will teleport utility. Two feats for at-will teleport (1, but trivially improvable in all the standard ways) is a better trade than two feats for an encounter teleport. I'd also recommend this method due to its synergy with lightning rush positioning, allowing you to choose an arbitrary square to command the battlefield from.
Also, runepriest is a trap. it has little to no stat synergy and no real mechanical synergy with battlemind.
Edit for increased details:
Objective: maximize battlefield mobility at level 9 as a half-elf battlemind. Dilettante should be used for marking and/or opportunity attacks. Multiclassing choice preserved, therefore con or wis for dilettante. No implements. Try to preserve feats improved init, valenar weapon training.
With HBE, that gives us 2 feats to work with, with one earmarked for "RP" purposes. Stats can be either con/wis, or con/cha. Given poster's emphasis on initative, speed of thought + quick reactions seems to have some nice synergies.
Persistent harrier provides teleportation mobility, especially with the fantastic harrying step.
Quick reactions chosen instead of improved init, allows complete dropping of dex focus and higher mobility first round. A move 7 + lightning rush means a delicious double-attack against enemy artillery when they choose to be silly. Optimally, this means eldritch strike, meaning far-marking is tricky. Powers selected to maximize advantages of high mobility. Most importantly "Lodestone lure" since there's no condition of adjacency for the player.
Soldier of the faith is fantastic. While it's not the requested runepriest, it's potentially an encounter-long mark at a distance. When combined with the initial mobility, it should fulfill the requirements. This also gives us holy symbols for a potential lark into implement classes. However, a cross-battlefield teleport is slightly redundant with the huge movement granted by speed of thought. While nice for bothering artillery and other folks who want to stay out of battle, this build already accomplishes that.
While nominally I'd recommend persistent harrier more, I believe speed of thought accomplishes the intent of this build more accurately. Fey-strike falchion chosen due to synergies with defending dabbler. While I feel that it's redundant in this build, there were no "must have" feats for level 8 and this does satisfy the question. Personally, I'd take defensive mobility for more choices during lightning rush. The other major problem with this build is that the defenses are a little soft, which just compounds the pain that speed-of-thoughting the enemy artillery will bring.
====== Created Using Wizards of the Coast D&D Character Builder ======
Psionic Study: Speed of Thought
Eldritch Strike: Eldritch Strike Constitution
Half-Elf Power Selection: Dilettante
FINAL ABILITY SCORES
Str 14, Con 22, Dex 10, Int 8, Wis 10, Cha 16.
STARTING ABILITY SCORES
Str 13, Con 18, Dex 10, Int 8, Wis 10, Cha 13.
AC: 24 Fort: 22 Reflex: 16 Will: 21
HP: 85 Surges: 15 Surge Value: 21
Acrobatics +4, Arcana +3, Bluff +7, Diplomacy +9, Dungeoneering +4, Endurance +12, Heal +4, History +3, Insight +6, Intimidate +7, Nature +4, Perception +4, Religion +3, Stealth +6, Streetwise +7, Thievery +4, Athletics +6
Level 1: Quick Reactions
Level 2: Valenar Weapon Training
Level 4: Heavy Blade Expertise
Level 6: Soldier of the Faith
Level 8: Defending Dabbler
Battlemind at-will 1: Twisted Eye
Battlemind at-will 1: Vicious Cobra Strike
Dilettante: Eldritch Strike
Battlemind daily 1: Living Fortress
Battlemind utility 2: Telepathic Challenge
Battlemind at-will 3: Lodestone Lure
Battlemind daily 5: Inconstant Location
Battlemind utility 6: Psionic Ambush
Battlemind at-will 7: Lightning Rush (replaces Vicious Cobra Strike)
Battlemind daily 9: Cascade of Rippling Force
Iron Armbands of Power (heroic tier), Dwarven Scale Armor +2, Fey Strike Falchion +2, Elven Cloak +2
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* The feat investment for defending dabbler is expensive, especially as battlemind doesn't come with implement powers. Adept dilettante allows the power to be rekeyed at the cost of the multiclass feat. Implements cost extra. As arotter notes: "Well, then it's already up to 2 feats (3 if you want to tackle the implement issue and that introduces an additional money/loot sink for the Battlemind). "